There is no "API" for creating an extended PC. An extended PC is created via @PersistenceContext(type=EXTENDED) which is inherently a container-managed PC.

An app managed PC is just that... managed by the app. In an app managed PC it is up to the app to configure things properly. That's kind of the meaning of app managed.

And no, its not a bug regarding IDENTITY.

So again, do what you want for extended (container managed) PCs. We are just pointing out how a container should properly configure the Session/EM for this - up to you if you want to take that advice.