With the "native" Session now being effectively an EntityManager, this now behaves in all effects like an EntityManager and this includes refusing to flush any update out of a transaction boundary. Such a "strict" check was previously only applied to users of the HEM module but now it applies to Session too because of the inheritance.

This is probably a good thing, although it might be a migration issue for users of the native Session API so it might be nice to introduce a property which would allow people to still shoot themselves in the feet if they highly wish for it.