[Rob1968]

I remember, several years ago, when the Fed changed the word "establish" to "obtain" in 4-23, because "establish" seemed to denote a process that could take an amount of time, in a guard trying to play defense against a ball-handler. Some thought that the defender was at a disadvantage, because contact with the ball-handler could come at different moments during the process.
So, as JRut and others have said, the moment of LGP being obtained allows us to make judgements on subsequent contact in a more uniform manner.
Two weeks ago, with a very good partner, we had seven PC calls in the first half, on team A, and two on team B. When the A coach commented on that fact, as we passed, at half time, I told him he must be pleased that his team was playing so aggressively. He didn't actually dispute whether the calls were correct. (His team was leading by double digits.)