The question here is why? What’s the point of this picture? The point of wedding photos is for the happy couple to have and remember their special day, and for relatives to put in their homes. So the question must be asked, why would you want a photo of your bridesmaid’s butt cheeks.
It’s possible there’s an inside joke going on here that we aren’t aware but other than that it’s just bizarre. It would almost make sense if the bride herself had a cheek exposed, but she doesn’t. Of course, she is supposed to appear matronly in her wedding dress white.