"they won't have to abide by the liquid carry-on rules." Not exactly true--all PreCk says is that the liquids don't have to be removed from bag. The 3-1-1 rule still applies.
Also, they MAY have to remove shoes but unlikely.
I believe TSA is dropping the Pre for FFs in the future. GE (includes Pre) and paid Pre are making the lines much longer but they move fast. UNTIL the people w/FF Pre are clueless, which is often the case, then everything slows down. I always hear savvy travelers tell the ignorant, "you don't have to do that" and the deer in headlights look proves how clueless they are...