Because he's their best receiver. They have actively been shopping McMichael also, FWIW.
So, no, I don't know for a fact. But I'd have to believe that the Dolphins aren't going to accept pick #93 for their best receiver who is signed for reasonable dollars. At that point, they'd probably take somebody else's 3rd rounder and not have to play him twice a year. Yes this is my assumption, although I am quite comfortable with it.
I did go back and read your posts, and must admit I didn't consider that option. However, in this case, I don't think it makes much sense for the Dolphins to accept a late 3rd round pick from a division rival for their best receiver and punt returner.