I know little about Ultimate meta. But this seems like cherry picking stats. Imagine playing the 45%win rate guy against the 55%. Just because the average is 45% for the one fellow doesnt mean that his chance in certain matchups is always 45%, it could easily be 0 in some cases. Conveniently Sakurai doesn’t mention the matchup win rates.
I think the main takeaway is that at the lower/intermediate skill levels, character selection is open. What you're talking about would only apply in the highest tiers.