Yea, takeing isolated winrates really tells much...
He got a 1,7%pickrate, which for one means the samplesize is hardly statistically relevant(not even 2k games played this patch), and even if it was, such a low pickrate bot means that the players useing them are experienced with yas bot, and they are most likely premade with a support that knows how to play that duolane aswell, and since you face him only once every ~60 games, people have hardly any eyperience playing vs him in bot, if you take in various supports, most yasuo+x combos probably are encountered only oce every 100-200 games, people just have no idea how to deal with it.
Him haveing that winrate is not because he's objectively to strong bot, but because he him self and his support mostlikely know quite well how to play the matchup while their opponents are totally cought off guard by it.
I had a ~80% winrate with leona+pant bot in S3, but that doesn't say anything how strong pant really is bot, it just was that me and my bro were a strong duo and well in sync regardless of picks and we kinda perfectionated this particular duo. We knew how to deal with all the standart lanes, but they had no idea how to deal with us.
Every once in a while though, we faced some that played the matchup right and it became apparent why pant wasn't a meta botlane.