Does HHH-11019 Open OPEN change the default flush mode?

We are only changing a particular check to additionally consider FlushMode whereas it used to not. The reason I reached out to you is because IMO WF really should set the FlushMode (or FlushModeType) to MANUAL for a PersistenceContextType#EXTENDED. Again, its obviously up to you whether you choose to do that. Just be aware that if you don't (and you may already be) then it is possible that INSERT commands (for IDENTITY generation) already occur, which can obviously happen during any of the one-or-more physical transactions that the extended PC participates in. That's clearly an error - the overall "unit of work" transaction can no longer be effectively rolled-back.

Because, the scope of app managed persistence contexts...

Why do you insist on bringing in scenarios other than extended PCs? The title of the issue explicitly discusses extended PCs. I've said multiple times that this is specific to extended PCs. Of course app-managed PC is different. It is also outside the scope of this discussion, as mentioned multiple times now...