This interaction has been there since Katarina got reworked almost 3 years ago. It consists of Yasuo being able to make the Bouncing Blade (Q)'s Dagger entirely disappear. In itself, it's not that big of a problem, as Bouncing Blade has a very low cooldown compared to Windwall, meaning you can easily bait it out and wait. Where it gets problematic is when the Q starts bouncing around minions for a moment after it actually landed on Yasuo. This basically means that he can wait a good second and a 1/2 after I threw the Q to decide whether or not he should cast Windwall. This requires no attention nor skill, as the Q is pretty much guaranteed to run into Windwall before reaching the ground.
Often, this will cause the Katarina player to shunpo when they see the Blade hit the Yasuo, as it's a very basic and regularly used combo. They'll then be left out with nothing to protect themselves or damage the opponent. In trades, it can cost a huge chunk of HP, and in teamfights (Even though it's easier to avoid when he has to use it against other spells from your team), guarantees your death. This is by far the most frustrating interaction I and many other Kat mains, and definitely deserves a Quality of Life buff.
Here is a very simple solution that would make this already hard matchup much more tolerable; Make the Dagger drop to the ground in front of the Windwall, similar to Braum E...Exactly like Braum E. This would still mean that the dagger isn't the best of spots, but if the Katarina decides to shunpo in, she still has the option to slash and reset her Shunpo.
As for Yasuo's counterplay options, I see it that way.. If the Yasuo decides to walk into the Dagger on the ground, it's purely his own and very much avoidable mistake, and he deserves the damage to his face. This should in no way be more unhealthy than the current way those 2 spells interact.