Blitzcrank E will hit through anything

I've noticed what seems to be a bug with blitzrank's e knockup. If you e a champ who uses an ability that should make them invulnerable, the knockup will still go through. I've played blitz and quite consistently, the knockup affects people in GA, Zhonya's, vlad pool, etc. In most scenarios, it doesn't seem to be very relevant although it is quite hilarious. Still, it's a weird bug that riot might want to look into.