To me, this seems like one of those things where if a bride or someone says, "You, don't do this!" I would roll my eyes and think them very dictatorial. But if I read from a neutral third party that "the advice is to not..." I would think, hmm, that's a good idea, I'll try to remember that.
Unless you are making people sign confidentiality agreements or something like that, I just don't think you can ask people not to post pictures of an event you've invited them to, that they took themselves. Personally I'm not ready to make that the standard. I think it's nice to wait until the HC post their own pictures, or to get permission from the HC first, but I don't think it's necessary.