It seems that the transactional client does not fully follow the JTA specification regarding CDI integration. Test in Narayana currently show divergence from

3.7 Transactional Annotation:
If an attempt is made to call any method of the UserTransaction interface from within the scope of a bean or method annotated with @Transactional and a Transactional.TxType other than NOT_SUPPORTED or NEVER, an IllegalStateException must be thrown.

What I can see there is difference between prior transaction spi and the new one in checking availability of transaction.
https://github.com/jbosstm/jboss-transaction-spi/blob/master/src/main/java/org/jboss/tm/usertx/client/ServerVMClientUserTransaction.java#L216
vs.
https://github.com/wildfly/wildfly-transaction-client/blob/master/src/main/java/org/wildfly/transaction/client/LocalUserTransaction.java#L59