I'm not familiar with Yas skills, but you can't automatically infer that because maxing one skill first is associated with a higher winrate that therefore you should max that skill first to get a higher winrate.
Specifically, sometimes it's optimal to max different skill depending on the matchup. If it is optimal to max one skill in a bad matchup and is optimal to max the other skill in a good matchup, and people play optimally, then maxing first skill first will be associated with lower winrates and maxing the second skill first will be associated with higher winrates. However, by assumption, you should still max the first skill in the bad matchup.
Let me see if I can give an example... As Nasus I always max q first. However, I sometimes max w next or e next. e shreds a lot of armor and is great for an all-in duel. It's also good for pushing lane if I won my lane and need to quickly put pressure on turrets. w is great at either helping me to escape, preventing an enemy from escaping, or reducing an enemy's attack speed.
Well, vayne and quin are hard counters to nasus because of their insane early-game bullying. Without a lot of jungler help, I have a bad time. They are auto-attack centric, and they won't stand in my spirit fire to duel me. So I max w (wither) second versus them. But because they counter me, I have a worse winrate laning against them. Also if a lane is going really badly and I need to be able to reliably escape from some other champion, i max w second. Consistent with then, Nasus on champion.gg has a higher winrate when he maxes spirit fire after q (rather than wither after q). That does NOT mean he should always max spirit fire second. It means that Nasus has a lower winrate when bad matchups force him to max wither second.