Officials are not interchangeable: individual umpires have measurably tighter or looser strike zones, and individual referee crews call more or fewer fouls, which shifts scoring and pace. Assignments are published shortly before games and almost nobody prices them. You keep per-official historical splits, and when an extreme official draws a game whose total or outcome market is sensitive to pace, you take the side their history supports.
Markets on Polymarket where referee & umpire assignment bias is the natural play:
