Wrong hole? Nope - it went exactly where he aimed it - right up her asshole. She obviously wasn't prepared, judging by her reaction -- but she didn't stop him as he was trying to get in in her ass, so likely not a stranger to being buggered.
I chuckled to my self watching his asshole open up as he was working his cock up hers. He's obviously been on the receiving end quite a bit. Perhaps his asshole was opening in sympathy for her's - or more likely in anticipation/longing to be fucked.