the human vulva is a bit more recessed between the thighs and buttocks

Funnily enough I had always assumed, from what I knew about how common face-to-face coupling was, that the entrance to the vagina would be further to the front than it is (so that the couple's hips would be about parallel). It was a surprise to me when I first actually encountered one and found that it's actually more recessed between the thighs.