You called it, Yoru coming out of Dimensional Drift inside of someone is the problem with the pass-through-stuff approach. Telefragging is a pretty extreme resolution.
But other solutions are...messy. Trying to push the two players away from each other when the Ult ends means one/both of those players is going to quickly move their position, essentially popping them from one spot to another. That makes any engagement (from any player's perspective) random and awkward.
Not to mention that popping players around in corners/against walls is an easy way to accidentally introduce issues with popping players through walls,