Using olaf ult on knockups like Vi ult will suspend you in the air longer than the original cc
I'm not sure what this is specifically limited to, but I know for a fact that pressing R at the right time to 'cleanse' a knockup (even though you can't cleanse a knockup) will suspend you much farther in the air and for a longer period of time.
This is most notably obvious with Vi ult. It's different each time. Sometimes she can move freely, sometimes she is stuck until it ends, but she never follows the animation.
Obviously it's not really intended to be able to ult knockups in the first place, but when a knockup is 1 second and pressing the ult to 'cleanse' it at the right time causes you to be suspended for 2 seconds, something is off.