I cannot speak for Everest, but grouping is difficult everywhere.
Now that I think about it, it may have been Rock n' Rollercoaster where we actually asked and were turned down.
It didn't bother us at the time, but after I got some responses to this thread I'm a little annoyed if front-seating requests are something that are supposed to normally be accommodated when possible versus something that's merely at employee discretion.
Like I said in the beginning, from what I saw in September the majority of Disney's coasters do not have the proper gates in place to allow the sort of front seat queuing at coasters at other parks, so if employees would prefer that guests not foul up the system by trying to hang back in the queue right before boarding I can understand.
If you can speak from a position of knowledge, what exactly is company policy?