Invalid POMs according to Maven XSD

The following POM(s) fail XSD validation against [1]:

• org/optaweb/vehiclerouting/optaweb-vehicle-routing-backend/7.33.0.Final-redhat-00002/optaweb-vehicle-routing-backend-7.33.0.Final-redhat-00002.pom
• org/kie/openshift-kie-jdkhttp/7.33.0.Final-redhat-00002/openshift-kie-jdkhttp-7.33.0.Final-redhat-00002.pom
• org/drools/camel-container-integration-tests/7.33.0.Final-redhat-00002/camel-container-integration-tests-7.33.0.Final-redhat-00002.pom
• org/kie/openshift-kie-hacep/7.33.0.Final-redhat-00002/openshift-kie-hacep-7.33.0.Final-redhat-00002.pom
• org/kie/openshift-kie-parent/7.33.0.Final-redhat-00002/openshift-kie-parent-7.33.0.Final-redhat-00002.pom
• org/kie/openshift-kie-springboot/7.33.0.Final-redhat-00002/openshift-kie-springboot-7.33.0.Final-redhat-00002.pom
• org/kie/workbench/stunner/kie-wb-common-stunner-svg-gen/7.33.0.Final-redhat-00002/kie-wb-common-stunner-svg-gen-7.33.0.Final-redhat-00002.pom

The error says: cvc-complex-type.3.2.2: Attribute 'combine.self' is not allowed to appear in element 'configuration'.

It is related to this part which is not allowed by the XSD (but can be done at the child elements, according to the XSD):

<configuration combine.self="override">

The above construct works in Maven, despite it is not allowed by the XSD.

[1] http://maven.apache.org/xsd/maven-4.0.0.xsd