It is true, it does seem as if her boobs are very far outwards guy's body. But if you look at the dude's cum animation, the cum starts spurting out of the bottom of the cleavage of the bottom girl's boobs, before his ejaculate drowns all of them inside the locker. Because of this, I think its an extreme version of a reverse paizuri instead of it being a deepthroat. If it was a deepthroat then the cum wouldn't come out starting from the bottom of the bottom girl's cleavage. Heres a gif of that if you want to take a closer look.
Also yeah it did ruin the scene a bit for me, had to stare at it for a long while and still didn't know so I had to post here. haha
Edit: I split the gif into different frames, cum definitely coming out from the bottom of the boobs. Seems MC'd dick is long enough to go through the huge tits of the bottom girl. dunno why i could not have thought of this earlier.