From the other thread to keep it in this place:
Firaxis changed from simultaneous OW to sequential because the users complained a lot about wasted shots.
I don’t know if this is the reason why SG does the same, but from my experience with the two Firaxis XComs I would not like to have simultaneous OWs in PP.
So here we are, two opinions and I still believe it is intended how it actually is designed and not a bug at all.
Not reacting on door openings … I have to test it, because, to be honest, I haven’t had any problems that you describe so far, so I don’t know.