https://docs.redhat.com/en/documentation/red_hat_jboss_enterprise_application_platform/8.0/html/migration_guide/preparing-for-migration-to-jboss-eap-8_default#migrate-jboss-eap-as-a-service_preparing-for-migration-to-jboss-eap-8

Chapter 2. Preparing for migration to JBoss EAP 8.0
"JBoss EAP 8.0 provides backward compatibility for JBoss EAP 7 applications."

This statement is explicitly false. EAP 8 is NOT backwards compatible with EAP 7 applications because of the javax->jakarta naming change.
It looks like this was a bad copy/paste from the EAP 7 docs that didn't get updated.