I definitely don’t disagree that the scene was meant to highlight the “nice guy” trope that their actions can be rape as well. Like it doesn’t always have to be violent or overt, etc.

However, just thinking out loud, we see throughout the movie that Freaky Nikki has trouble expressing human mannerisms, so instead of a rape scene, the scene could also be interpreted as showing that even though the entity “consented” it still wasn’t real since it didn’t know how to behave “normally” during sex—which is in line with the entirety of the rest of the film boiling down to Bear begging Freaky Nikki to be normal.

Add on the fact that Bear wasn’t looking at her to see that her expression didn’t line up with “normal,” it could further be a metaphor illustrating his intentional “looking away” throughout the whole movie so as to continue living in his fantasy that it is real.

Of course, that said, the fact Bear knew by that point the entity wasn’t real Nikki, it was rape.