I think it is pretty clear that Beane didn't like Worthy or Legette enough to avoid making the deal - otherwise why not just pick them? It's possible that Pearsall was one of their targets (no way to know), but even if yes, probably one of several targets. It sounds like Beane was high on the big 3 plus Brian Thomas, but was not willing to give away the farm for any of them. There are probably several WR that Beane has in this range that he would consider picking and can't really make up his mind which one.
My own inclination is that if they have to pick here, it will be either DeJean or Powers-Johnson, and I think DeJean is the most likely, with the plan being to move him to safety, where he would probably be a Day 1 starter. I don't think the Bills view any of the remaining WR as a Day 1 starter, which is why they are willing to go back rather than pull the trigger. DeJean is the consensus BPA regardless of need, and safety is a big need for the Bills, so to me that makes the most sense here.