Skarner ult gets canceled

as a skarner main i know alot about skarner his q passive, best builds, lore, and especially how his ult works. . . but what i saw on PBE today baffled me never before has my ult ever been canceled unless i was killed, like i mean never been canceled, while ulting someone i have been caught in a zyra ult, a yasuo ult, a lee sin has kicked me miles away and the person i ulted is yet still being impaled, and come with me no matter what happens, but today kalista would ult her oathsworn ally and save them from the clutches of my stinger. from what i understand when she activates her ult, her ally is untargetable, but i dont believe it should remove suppreses if i am correct. i believe this maybe a bug not completely sure but just wanted to make sure because so many times i would ult the enemy zyra, sona, lux. and kalista would simply ult back and save them from being completely murdered by my team while i drag them into tower.