Blame it on a version of "he's always done that" syndrome.
I asked an Eastern League crew about a similar move I saw in their game. Their response was along the lines of, "He's made it dubs without that being called in single A. We're not going to be the ones to tell him umpires in three leagues and their evaluators screwed up, and when he gets to trips, they won't tell him either."
So he makes it to the Show and continues the move that no one called. (Until he meets up with balkin' Bob, of course.
)