The EJB3 subsystems is untested for transformers. It gives out false impression since there is a test class called org.jboss.as.ejb3.subsystem.Ejb3TransformersTestCase which contains some of the testing infrastructure pieces, but those are NEVER used and thus never tested.

https://github.com/wildfly/wildfly/blob/37.0.0.Final/ejb3/src/test/java/org/jboss/as/ejb3/subsystem/Ejb3TransformersTestCase.java#L92