this is actually a really dumb/needless mechanic that changes practically nothing. Yas Rarely has (at least in solo queue) more than one other person on his team with knock ups anyway.
added complexity to gain literally nothing in the long or short run.
Yasuo getting to ult off of other champions knock ups is probably one of the LEAST complained about parts of his kit.
if you look at why people dont like playing against him, its almost always his dmg (via crit passive), shield (laughable, but people will complain), Mobility ("infinite" dashes...), or his safety when he ults (refreshes shield, puts at max range outside of turret aggro if able... forget that he is self stunned the whole time). A LOT of the time, its his windwall.
On a few occasions, his low cooldown on Q/E comes up.
Personally, I think Yas is a fine champion, though I understand why if you play certain other champions, he can be VERY oppressive/annoying/difficult. But such things are largely subjective. I for one hate playing against things like Heimmerdinger, or Urgot. Id much rather fight against Yasuo. But again, thats just my opinion.