People having to label something ATG doesnt really say anything besides that that lifter has better mobility than another one who still get deep enough. It is pretty simple, either it is a squat, or it is not. Its not MORE of a squat just because someones stance, physical attributes and/or mobility gets their but closer to the floor. At the end of the day, the crease of the hip is below the top of the knee.
So in most cases, someone saying its ATG is really just saying "that lifter is pretty weak, but he is flexible" or whatever. And ATG is a subjective term as it is not defined as anything. So that means (and im just talking about good depths here) that lifter X and lifter Y both go as deep as they can, lifter X is deeper, but they are both ATG.
So to throw a little fuel on the fire, ATG is a term weak lifters use to justify their light weights, when they should be occupied with just getting stronger. There is no shame in not squatting 500 lbs, everybody gotta start somewhere. But dont make excuses like ATG, or so and so. I have the utmost respect for a guy batteling 225 lbs in the gym to get stronger for himself, where i lose it is when he starts talking about how they are ATG. I take they are deep enough as a prerequisiste for calling it a squat, i dont need to know how many cm your ass is away from the floor.