Bard Ult inconsistent

Playing a game earlier today as Bard, I ulted a Tahm Kench as he ulted in. However, to my dismay, even though I made sure that the ult connected after Tahm emerged, it hit when he was still in the air and thus had no effect. Seeing as I have frozed Darius while in mid-dunk, this appears to me to be inconsistent, and should either freeze everyone in the circle or just those on the ground.