I am at work, so i cant watch the video right now, but ill say this about genetic potential. Genetic potential means the most amount of muscle you can carry on your frame in a natural state or on trt (within the physiological range). It is obvious and common sense that it is technically impossible to maintain an unnatural state of muscle mass by staying in the physiological range. With that said, most people, even on gear, dont reach their genetic potential and dont realize just how high that is. A general rule of thumb is that nobody, even the genetic elite can maintain a FFMI (fat free muscle index) naturally higher than 25. That seems to be the upper index on a natural bodybuilder with elite genetics. Steve Reeves, one of the greatest true natural physiques of all time had a FFMI near 25
As an example, I haven't even hit my genetic potential so I can maintain my muscle mass with trt just fine. Last time I checked my FFMI was somewhere around 23-24. I'm 5'9" 195 and 8% bodyfat
So, yes....guys like Phil heath, Kai Greene, Ramy, and basically anybody at the pro level are way above genetic potential....even some classic and physique guys are. That means they need to cruise higher to keep that level of mass and stay in the superphsiological range. Look what happened to Jay Cutler as soon as he retired. He didn't quit training. He still works his ass off, and still looks great....but he dropped well over 50 lbs of muscle. He said himself in an interview that he's more concentrated on his health and fitness than anything now. He's a smart guy. He had his day, did it, and now it's time to be healthy. I'm sure he is on regular trt doses and his body is just going to his genetic limit, which is obviously on an elite level and higher than 99% of the people. Even then he still lost a lot. That's just reality and how hormoes work. You can't maintain a on unnatural body on natural hormone levels