Besides yas being able to ult the knocked up champion, is there any difference between stunn and knock ups? Also is there a reason why there are no other champions that have interactions with knockups or other types of cc?
Stuns can be cleared by cleanse, QSS, and things like GP's W. Stun duration is also reduced by tenacity.
Actually there is another champion who interacts with CC! As long as Nocturne has at least one rank in his E, he gains 175% move speed when moving towards feared targets (including fears from any other champion)
Knockups can not have their duration reduced by tenacity, and you can not break out of them with QSS, cleanse, or any other CC cleansing effect. In effect, knockups are stuns that can not be mitigated or broken.
is there a reason why there are no other champions that have interactions with knockups or other types of cc?
You have to design a champion around it to some degree, and it usually isn't worth it. Yasuo has the interaction primarily to give him a different access to his ultimate when he's by himself than when he is in a teamfight situation.
Knockups are also the ideal CC to be designed around. Other types of CC are either so ubitiquous that they don't serve as effective limiters of an ability (stuns, slows), or they're rare enough that the champion can't realistically expect to be paired with someone that has the mechanic (silences, roots). They also lack the kind of visual clarity that a knockup has to alert the champion that his allies have set up his ability (a champion popping up is much more visual than a champion getting silenced).
