Using Q on an enemy with three stacks of passive gets rid of the passive. Boom, no more getting stunned then instantly swallowed only to get stunned again. Notice every other champion in the game with a passive like that gets a reduced effect for multiple uses or can't use the effect multiple times against the same enemy.
Lost R1 votesYou know swallowing champions consumes the stacks?
The Bearded Bard1 votesThen why shouldn't Q?
xFrostKnightx1 votesBecause the stun is needed to get close enough otherwise you can kite for as long as he doesn't hit Q.
If it had a Cd on stun, but left stacks it'd be fine.
MalzaharAnyLane1 votesI don't ever have this problem playing Tahm, if I've landed a third stack I'm either close enough to not care about casting Q or landed the third stack by casting Q.
The passive is supposed to be consumed on stunning with Q, it's an oversight that Q doesn't clear stacks.
Lost R1 votesWhere did you read that? If it was a bug, it would have been caught by now.