It is but one of several factors that archers will tinker with in order to reduce PO. As reddogge points out, it's also one of the least significant. The difference of 1" in your sight picture is going to be minimal, if noticeable at all, but every little bit helps. Most combinations will yield a PO in the 40 yd or greater range...getting that to a PO at hunting/3D ranges of 20-25 yds. requires some effort. Let's see, I went from split to 3U, index to middle finger anchor, intentionally high nock sets, heavier arrows and a 3/4" crawl to get there....but I'm there, and I started with a roughly 2.5 foot gap @ 20 yds.