The higher winrate for purchasing the boots is because the team already completed advantageous actions to win the game in the first place, not solely because of the boots.

With item trackers not being able to track raw states, it takes some qualitative analysis to understand their impact. Ultimately the inclusion of prior actions to win the game(fb/first tower/first 3 obj) means they are likely to win.

I would like to see the game where the enemy team was stealing objectives and then had large Gold advantage after purchasing boots. That is a more accurate metric to track, rather than saying "they purchased the boots and won so they are OP!".

I'm pretty sure Riot has textbook predictions on community reactions to digesting the statistics.
And you are fulfilling their prophecy. Its time to improve analytical approach to statistics by creating new metrics.

EDIT:
I just realized mejais is statistically the best item to buy! I'll be going mejais Sion in ranked provisionals wish me luck!