It is similar to how when you say the word "poop" your mouth does the same motions that your butthole does when you poop.
And when you yell "explosive diarrhea" your mouth does the same...
"Cloacal Kiss" yeah I'm no scientist but I think the analogy holds true.
I've never seen someone else play D&D without being absolutely baffled at what kind of rules they use.
Come to think of it, it's not that rare to play a game like Settlers of Catan or even Uno with new people and also find that they have been following completely made up rules without realizing it.