We have had so many discussions on this board about calling balks, or when not to call a balk. I have always been in favor of, if you see a balk, call a balk! Especially early!
I think arguing to U1 about it was the wrong choice. U3 and PU had a much better look at it. Not that it would have made a difference. I love the way PU said he didn't see it. At least that what it looked like his lips said.
He does have an excuse, he is an umpire so you know he's blind