Challenging Smite vs Vayne Doesn't Work

In this game, Vayne was getting pretty far ahead so I went with Skirmisher's Sabre in order to keep vision of her during fights. The description for Challenging Smite says it "reveals champions for 4 seconds". During several fights against the Vayne, I would smite her and she'd still go invisible while Tumbling during her ult. At one point she even went invisible, attacked, walked into an unwarded bush and was revealed, then tumbled and went invisible again. Is this the intended functionality?