CF talks about the importance of the half-squat and not so much full squats. I get the impression that he doesn't really give a shit about ATG squats so I kind of doubt that the 600x6 was ATG.
Not that it matters, dude was still fast as hell.
ya, and most sprinters aren't going to have the best natural "ability" at ATG anyway, due to the leg length.
though, when most people think squat they automatically think "ATG", so, it's nice to clarify.