sub-transaction with spring JpaTransactionManager does not work as expected

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:camel="http://camel.apache.org/schema/spring"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd       http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
    <bean class="sample.MyCarProcessor" id="myCarProcessor"/>
    <bean class="sample.MyBicyclePrcessor" id="myBicycleProcessor"/>
    <bean class="org.apache.camel.spring.spi.SpringTransactionPolicy" id="PROPAGATION_REQUIRES_NEW">
        <property name="transactionManager" ref="transactionManager"/>
        <property name="propagationBehaviorName" value="PROPAGATION_REQUIRES_NEW"/>
    </bean>
    <bean class="org.apache.camel.spring.spi.SpringTransactionPolicy" id="PROPAGATION_MANDATORY">
        <property name="transactionManager" ref="transactionManager"/>
        <property name="propagationBehaviorName" value="PROPAGATION_MANDATORY"/>
    </bean>
    <camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
        <route id="parent-route">
            <from id="route-timer" uri="timer:foo?repeatCount=1"/>
            <transacted id="transactionA"/>
            <log id="_log1" message=">>> call rollback-route"/>
            <to id="_to1" uri="direct:rollback"/>
            <log id="_log2" message=">>> call commit-route"/>
            <to id="_to2" uri="direct:commit"/>
            <log id="_log3" message="done"/>
        </route>
        <route id="rollback-route">
            <from id="_from1" uri="direct:rollback"/>
            <onException id="_onException1">
                <exception>java.lang.Exception</exception>
                <log id="_log4" message=">>> rollback-route's' onException block. mark rollback"/>
                <rollback id="rollbackA" markRollbackOnlyLast="true"/>
            </onException>
            <transacted id="transactionB" ref="PROPAGATION_MANDATORY"/>
            <process id="_process1" ref="myCarProcessor"/>
            <to id="_to3" uri="jpa:io.fabric8.quickstarts.camel.Car?usePersist=true"/>
            <throwException
                exceptionType="java.lang.IllegalArgumentException"
                id="_throwException1" message="Forced"/>
        </route>
        <route id="commit-route">
            <from id="_from2" uri="direct:commit"/>
            <onException id="_onException2">
                <exception>java.lang.Exception</exception>
                <log id="_log5" message=">>> commit-route's onException block"/>
            </onException>
            <transacted id="transactionC" ref="PROPAGATION_REQUIRES_NEW"/>
            <process id="_process2" ref="myBicycleProcessor"/>
            <to id="_to4" uri="jpa:io.fabric8.quickstarts.camel.Bicycle?usePersist=true"/>
        </route>
    </camelContext>
</beans>

CREATE DATABASE sample;
create table car (
  id integer, 
  name varchar(10)
);
create table bicycle (
  id integer, 
  name varchar(10)
);

09:28:59.345 [main] INFO  i.f.quickstarts.camel.Application - Started Application in 5.082 seconds (JVM running for 5.464)
09:29:00.409 [Camel (MyCamel) thread #1 - timer://foo] INFO  parent-route - >>> call rollback-route
Hibernate: insert into car (name, id) values (?, ?)
09:29:00.446 [Camel (MyCamel) thread #1 - timer://foo] INFO  rollback-route - >>> rollback-route's' onException block. mark rollback
09:29:00.448 [Camel (MyCamel) thread #1 - timer://foo] WARN  o.a.c.processor.DefaultErrorHandler - Rollback (MessageId: ID-fedora-1703636938098-0-2 on ExchangeId: ID-fedora-1703636938098-0-1) due: Forced

Message History
---------------------------------------------------------------------------------------------------------------------------------------
RouteId              ProcessorId          Processor                                                                        Elapsed (ms)
[parent-route      ] [parent-route      ] [timer://foo?repeatCount=1                                                     ] [       105]
[parent-route      ] [transactionA      ] [transacted                                                                    ] [         0]
[parent-route      ] [_log1             ] [log                                                                           ] [         0]
[parent-route      ] [_to1              ] [direct:rollback                                                               ] [         0]
[rollback-route    ] [transactionB      ] [transacted[ref:PROPAGATION_MANDATORY]                                         ] [         0]
[rollback-route    ] [_process1         ] [ref:myCarProcessor                                                            ] [         0]
[rollback-route    ] [_to3              ] [jpa:io.fabric8.quickstarts.camel.Car?usePersist=true                          ] [        33]
[rollback-route    ] [_throwException1  ] [throwException[ref:null]                                                      ] [         0]
[rollback-route    ] [_log4             ] [log                                                                           ] [         0]
[rollback-route    ] [rollbackA         ] [rollback                                                                      ] [         0]

09:29:00.449 [Camel (MyCamel) thread #1 - timer://foo] WARN  o.a.c.s.spi.TransactionErrorHandler - Transaction rollback (0x5f1eff72) redelivered(false) for (MessageId: ID-fedora-1703636938098-0-2 on ExchangeId: ID-fedora-1703636938098-0-1) caught: java.lang.IllegalArgumentException: Forced
09:29:00.449 [Camel (MyCamel) thread #1 - timer://foo] INFO  parent-route - >>> call commit-route
Hibernate: insert into bicycle (name, id) values (?, ?)
09:29:00.458 [Camel (MyCamel) thread #1 - timer://foo] INFO  parent-route - done
09:29:00.461 [Camel (MyCamel) thread #1 - timer://foo] WARN  o.a.c.s.spi.TransactionErrorHandler - Transaction rollback (0xbaf87a5) redelivered(false) for (MessageId: ID-fedora-1703636938098-0-2 on ExchangeId: ID-fedora-1703636938098-0-1) caught: Transaction silently rolled back because it has been marked as rollback-only
09:29:00.463 [Camel (MyCamel) thread #1 - timer://foo] WARN  o.a.c.component.timer.TimerConsumer - Error processing exchange. Exchange[ID-fedora-1703636938098-0-1]. Caused by: [org.springframework.transaction.UnexpectedRollbackException - Transaction silently rolled back because it has been marked as rollback-only]
org.springframework.transaction.UnexpectedRollbackException: Transaction silently rolled back because it has been marked as rollback-only
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:752)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:711)
	at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:152)
	at org.apache.camel.spring.spi.TransactionErrorHandler.doInTransactionTemplate(TransactionErrorHandler.java:182)
	at org.apache.camel.spring.spi.TransactionErrorHandler.processInTransaction(TransactionErrorHandler.java:140)
	at org.apache.camel.spring.spi.TransactionErrorHandler.process(TransactionErrorHandler.java:107)
	at org.apache.camel.spring.spi.TransactionErrorHandler.process(TransactionErrorHandler.java:116)
	at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:201)
	at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:201)
	at org.apache.camel.component.timer.TimerConsumer.sendTimerExchange(TimerConsumer.java:197)
	at org.apache.camel.component.timer.TimerConsumer$1.run(TimerConsumer.java:79)
	at java.base/java.util.TimerThread.mainLoop(Timer.java:566)
	at java.base/java.util.TimerThread.run(Timer.java:516)