Does winrate statistics for champions matter or not?

It has no effect on potential. It is a measure of said strength.

And, yes, winrate matters. It's not the only thing that matters, but anyone who says winrate doesn't matter (in terms of balance) is simply lying.

i think its annoying when they choose who to nerf and buff for example they can nerf teemo to the ground and it doesnt make him any less of a bitch to fight against just because he doesnt have a super high win rate doesnt make him any less annoying

There are special snowflake champions that even if the win rate, pick rate, and ban rate, scream for an immediate nerf, it won't matter. Aside from those, win rate does matter. Specially when you check high elo top 20-30 best players on the champion that is being pick/played.

It's an estimated number.

Riot are the ones with the REAL winrates but they don't share them to the public.

They do, but you have to look at context. Why is the winrate high? Is the playrate high? Usually high play AND winrate mean that a champion is performing too well, as the law of averages would even it out at 50%, though there are many different reasons why that might be the case.