I've noticed... since i've lost 2:3 home match against much weaker opponent (lol)
4-5-1 has a weakspot playing against 3MC. No matter of possession stats, the opponent seams to have around the same chances as me. First game i won 0:4, but i guess it was just the odds, cause i had 4 more saves and 2 on goal shots than him. I've noticed the same in league matches... If player have 3MC (5-3-2 flat, 4-1-3-2) he will have much more chances than you.

So please post if you can prove this or not