Well, they are up front about that they want, so no surprises there. And if photographers don't want the assignment, they don't have to answer the ad!
They are presumably adults, since they're entering a marriage, and obviously it was important to them they save themselves for marriage. Therefore, since it seems to be so important, is it really that different than the exchanging of rings?
They didn't invite anyone else to watch. They didn't say they're planning to sell them or show them to other people. Maybe they haven't gone all the way, but certainly they know what turns them on.
Not your wedding or sex life, so who are you to judge?