IIRC, they certainly go over your initial application and tell you whether or not you are competitive. Whether the Congresscritter reps check on that is unknown, but in the grand scheme of things, remember this:
The nomination IS the first great hurdle that MUST, except in the rarest of circumstances, be cleared before having ANY chance to get into the Academy. The Academies are highly selective, and the Congresscritters know it. Additionally, it does the Congresscritter no good to nominate people who drop out later, so it is in their best interests to select the best.
So, whether the Academy does a semi-official "first cut" is pretty irrelevant because the REAL first cut is the nomination, and those are not given out to folks with 1.7 GPA's.
Hope that helps.
ETA: Hopefully, one of our resident BGO's will be along soon to clarify any nuts and bolts I may have missed. I don't think the general jist will be any different, though.