When playing One for All as a team of Yasuos, our team suddenly noticed something quite nasty. We had to play against a team of Gangplanks and whenever one of us ulted Gangplank, he just walked out of the ultimate after eating some oranges and the rest of us could no longer ult him.
Scurvy cannot remove airborne CC but it can remove stuns. To me, it seems Yasuo's Last Breath does not count as airborne CC as GP can just walk out of it after eating oranges. He just cancels the ultimate and puts himself back on the ground.
But then again, how can other Yasuos still ult a target that is already ulted if it's not airborne CC?