Oh boy first PRC post, warning: lot of (rambling) explanation will come before position
I've always had some qualms with the way that CAP handles poll-jumping as a whole. Obviously, we need to segment the process. Otherwise, there would be so much sheer uncertainty floating around at all times that we could never get anything done. But sometimes there are places where the whole is more than the sum of its parts - where the stat spread /just won't work/ without this ability, or that typing is just so perfect for the concept but only if it gets this move. In those cases, i think that the voters choosing one means they de facto agree to the other, and yes it's polljumping, but it's integral to a hollistic Pokemon. Otherwise it looks like we took a doll (nothing personal voodoom) and stapled on all these separate sheets of paper in an attempt to make it a Pokemon. This happened in this project as recently as RD's stat spread which assumed Drought (don't ask me how one got in without the other).
However, while competitive-competitive links follow easily, linking flavor and competitive pieces together is more fuzzy. Competitive is supposed to be completely unaffected by flavor, unlike by other competitive portions. By voting for a movepool which has the best competitive aspect but perhaps does not agree with their flavor ambitions, a voter is de facto ushering in a flavor they disagree with because they preferred the competitive aspect - which is supposed to be the sole factor of a movepool vote, as it's competitive.
Unfortunately, we don't have perfectly competitive voters, so that line of logic throws us for a loop. In a utopia, voters in competitive portions would place aside all flavor concerns, but as we see from many users voting against Cape's movepool purely because they disliked the event flavor, that ain't what happens. As someone who cherishes the competitive aspect of CAP, letting a competitive submission lose because of flavor reasons is a cardinal sin. If someone voted against a movepool because it implied a prevo and they didn't want one (or vice versa) it would be counterproductive to making the best Pokemon possible. Furthermore, i wouldn't want the userbase voting in a movepool that is the best competitively but has a flavor they almost all hate. It's easy to adjust movepool flavor to fit a prevo's existence without changing anything competitive about the movepool - and then we're removing one confounding factor in a movepool vote, which is always a good thing.
So yes, i'm in favor of an early prevo vote, because it helps contribute to the best competitively minded Pokemon possible with the least accidental flavor-based interference