Why hasn't Riot considered changing Yasuo's ultimate armor pen to scale per rank of ult?

It seems following the mid-season update Yasuo's ultimate bonus armor penetration went untouched when other penetration items lost stats and tank/bruisers items lost health, but increased in resistances. I main the champion (feel free to devote for this reason and this reason only), but playing against it, the 50% bonus armor penetration is quite powerful early-mid game when he had crit components for PD/Shiv or PD/Shiv themselves. (either 20% crit with brawlers glove, 40% with zeal, or 60% with PD/Shiv) he is getting the bonus armor pen (which lasts for 15 seconds) on a sizable portion or majority of his auto-attacks or Q's depending on what items he has early-mid game.

In my opinion, it should scale with each rank up of his ultimate, starting at say, 20, then going to 30 at rank two of ultimate, and then 40 at rank three. This would put it in line with other penetration items (while still being better than LW build paths by 5%). If Riot wanted to keep the 50% bonus armor penetration for later in the game, they could do 20-35-50, at each respective rank (or even 30/40/50 as someone from /r/yasuomains suggested). I think this would allow better counter-play for top-lane (since that seems to be the problematic lane) since he wouldn't be able to duel tanks so effectively with only PD/Shiv components or PD/Shiv themselves. Even more so with Zeal and IE being cheaper. I believe this would bring him more inline with the meta and other picks at the moment, since he gained a ton from the mid-season update while losing very little. This is the one thing I'm surprised Riot has left untouched for all these years on Yasuo, and if they move forward with other nerfs, I highly encourage them to consider this change before messing with his Q, W, or E again.