Yasuo vs Olaf bug

Posting this here because I believe this is bugged and not working how it should. I never play as but tonight I did for the heck of it.. Ulted olaf while he was in his ult.. I understand olaf cannot be disabled, but yas should be able to hit him 4/5/6 times.. Really sucks to ult olaf, see the message cannot be disabled but don't hit him any of the times.. Maybe it is working as intended and if so, glad I don't play yas. I get olaf can't be disabled which is cool, shouldn't negate any damage that should happen. Damage should still go through just not the cc part.