Yes you'd have to witness it to really know what went on. I think it was said the squats were buried as deep as possible but "ass to grass" means different things to different people. "No rest" as well as you say. I know if I did a leg press and leg extention to failure first I couldn't even hit 225 for one in the squat. My squat strength would drop by more than 50% easily.
I don't think anyone could even
regain 63lbs of muscle in 28 days with all the gear in the world. Milos cited some unbelievable number for Flex Wheeler but it might have been "just" 30lbs or something in 4 weeks, can't remember exactly, and Flex ended up in the hospital.
A while back all time world record squat holder Joe Sullivan tried to beat Tom Platz' squat record but came short even
after prepping for it for months. I'm not saying Tom's set wasn't legit but if it was it was crazy. Unfortunately the people involved in the event made many doubt it. I think there are actually many who could it, strongmen etc, maybe even some bodybuilder, but I think they are much heavier probably?