What we don't know (maybe a resident WS searcher can verify?) -- we don't know if the searchers were "on the scene" or on the road because we haven't seen any footage until after the news broke.
DM indicated more than once that EG was the "key" and that it was important that she find Lucas.
I thought in one of his interviews DM indicated he was trying to make EG believe that "people knew" where Lucas was and they were going to find him imminently.
I'm guessing that his earlier interactions with the searchers gave him enough confidence to invite them on the scene -- they hadn't publicly disclosed their search locations, shared info with LE and TXEQ, they were trained not to disturb evidence, and their personal interactions with DM may have given him a good read on their trustworthiness to be present for whatever purpose he had in mind.
While I wish they would all stop talking to the media, DM seems careful in what he will and won't discuss for the most part and I can't help thinking that their presence either during or shortly after the discovery had everything to do with his angle to work EG OR to have them more thoroughly search areas he wasn't sure about that he and EG had already passed.
Could've been psychological warfare on EG, or it could have been a courtesy to searchers who have given so much. Hard to say.