I believe his point is that UR functions similarly to a hard stun, but not as effective. He is both correct and incorrect in this statement. He is correct in that you could stun someone when you have almost no health and beat on them for 4 seconds to win the fight just as easily as popping UR. The negative to UR is that it can only be done at the end of a fight without sacrificing massive amounts of health, so it is indeed less effective than a stun. The downside to a stun, however, is that it only affects one opponent whereas UR mitigates damage by 99% on anyone who happens to attack. In a 1v1 situation, the stun is better, but in a group setting UR is still a superior ability.
Yeah but UR has a LOT more used than winning a 1v1 fight. We are talking godmode ability for objectives here. Nothing close to a hard stun at all.