From all the interesting things in this thread, there is something, an idea, that does not connect woth me at all. I really don't get why people think it was butt sex.
In my experience you can very easily have vaginal sex with a woman from behind.
On the other hand, I would assume anal sex needs careful preparation with lube. That was not in part 2 at all.
If it was in the vagina or in the butt is of course a non issue for what part 2 is about. But I have seen this so often now, that I felt I had to say something.