That's also why in a tournament (or a showmatch) you'd play the same opponent in a series (like best of 3, best of 5...). I once had a couple friendly games with a dude in masters 3 (that's maybe 1K MMR above me) and... actually won one map. My mechanics are pretty bad, but I have a very decent understanding of the game. He tried something funny - I scouted, responded, and killed him. If it were a best of 1, that was our first map - I would have won the series.

This would not happen with Serral. He does lose against other pros, but not against joes. When you face an opponent 1.5K MMR below you, you're putting something like -200MMR on the table if you lose. You can't stay 200-300 MMR above the #2 spot if you ever drop a game like that.