In EAP 7.1.0.DR15, we have

• docs/schema/jboss-ejb-client_1_2.xsd with URN urn:jboss:ejb-client:1.2 and this is meant for the jboss-ejb-client.xml file which is used for matching remote-outbound-connections for applications, and
• docs/schema/jboss-ejb-client_3_0.xsd with URN urn:jboss:ejb-client:3.0 which is, IIUC, meant for client configuration (wildfly-config.xml).

Therefore we have a name clash of two namespaces which aren't used for the same thing.