Gameplay: Galio ult not cancelling tp

So teleport has always been cancelled by silence, stun, root, taunts (I thought), and displacements. Twice now I have attempted to use and failed to stop an Enemy Teleporting away. As far as I can tell Galio ult fits the criteria to force an enemy to stop Teleport. Enemies are taunted forcing them auto attack Galio (can't AA when TP'ing so this force should disrupt ranged champions). Galio ult forces players to "move" into melee range so a max range catch on ult or even less should force the players to walk at galio and cancel the Teleport. Not sure 100% if this is a bug but based on the mechanics of the ability and the summoner spell it appears to be so.