While I agree that a very small amount of movement would be trifling and not really make a difference, once you allow the ball to be moving, you have to think about the consequences. If you simply say the ball is allowed to be moving, with no further conditions, then what's to stop a team mate kicking the ball back from ten yards away? As we all know, you can get better distance/power by kicking a moving ball. If you don't want to allow that, then you have to place restrictions - but what should those restrictions be? How far, how fast and in what direction is the ball allowed to be moving? You can't just leave it completely open, so what are you going to set as limits?
I think with the above, we use our experience and judgement and reading of a situation and decree whether the ball still wobbling is a threat, or potential threat, to our match control, in the same manner as a throw 5/6 yards up park, or as we see all too often, 10/12 yards down the park, from where the ball actually went out.
Also tempo of game, is it a fast enjoyable sporting encounter where things are going fine and rapport is good and everyone is playing spirited or is it highly strung and doing everything to keep things controlled is required, so whilst no, there is no allowance parameters, we use our own tolerance which we feel is in keeping with the game.
With experience, good reading of the game, and the all important, luck, everyone just gets on with it and is happy to do so.
clearly on the flip side 1 in a 100 the end result might well be goal and someone somewhere will take the passage in play back to a moving ball 70 yards down the park, but as we keep saying, football is not an exact science and it could easy have been a "soft" foul not given in the same spot on the park and 10 passes later and 70 yards it becomes a goal....thems the breaks.
I have another take on moving ball too
A moving ball deep defensive which ref is aware/unaware of,yet kicker misplaces it and it goes out of play, or, even, player he passes it to misplaces and it goes out
Is any ref then going to be grateful for the AR flag going up to order a retake of the fk?