Nobody else would be cleared to G or F on the other side of runway 4L when JFK is landing 4R.
Maybe someone was cleared from Z to G to hold short of 4L. Maybe it was an airport work vehicle. What it may have been doesn't matter. The point is, that the controller asked him to hold short of G for a reason. You don't know what that was, so you can't claim that it was much ado about nothing. And the controller has to make sure that he doesn't have disoriented pilot.
Far and away most accidents occur on the ground and many accidents start out as something unrelated that causes a distraction. You don't want a small misunderstanding to snowball into a tragedy.
I suppose the original post was one to point out mutual consideration and respect between the controller and pilot, but I still agree with silvercreek's assessment.