Conquest always matches up #1 vs. #1, #2 vs #2 and so on. It's based off of the order they are in when you select your pitcher, not the order they're in on your Team Management Screen. Play Vs. CPU always had them off set. In 2020 it went #5 (You) vs #1 (CPU), #4 vs. #5, #3 vs. #4 and so on. I think in 2021 they either reversed that order or bumped it down 2 Positions? I'm not 100% sure. But you also gotta remember after Roster Updates, those positions can change. And when you're dealing with teams that have multiple common SP's all around the same overall...it depends on who their actual starters are. Some of those guys are on the 40 man roster, but they may not be in the actual rotation. I'm sure some teams may have a 62 Wade Miley type as their #5 starter instead of some 63 or 64 no namer that has no MLB experience.