mentzer trained like everyone else did to get his size. maintaining it he did heavy duty but not one set per bodypart. he pyramided up like everyone else but only counted the last set as the only set. he found a niche that people would believe and buy into it. what the mags said was bull but kinda true too. saying arnold did 2 hours or more each day for 6 days etc was kinda true but ONLY before contest time. rest of the time was 45 min to and hour 3-4 days a week. same as everyone did from my time. mentzers system sounds good on paper and DOES work a little bit as will any new training system. but you get used to it and with his ( as he wanted people to do it) you burned out way to quickly. good for an occasional workout when time is limited. yes he had great genetics. yes he used alot of drugs yes he used street drugs and smoked. everyone back then had mail order courses and t shirts to make money. mentzer had a great idea and no one else was selling it. case closed.
You know all this how? Did you personally watch Mike train or even train with him like MaxRep did? You were able to keep track and witness Arnold's training routine of 3-4 days a week 45min to an hour?
You seem to lack a basic understanding of Mentzer's/Jone's training theory as recovery was one of the hallmarks of their protocols which were spaced out to avoid being "burnt out" (over training). You are far more likely to "burn out" training six days a week two hours a day than Casey's 3 days a week 25 minutes workout during the Colorado experiment.
It should also be noted that one of the reasons he went to Arthur Jones was to due to his lack of progress with conventional training and it was only after meeting Viator and Jones and spending time with them that you can see the progress he made. Progress he documented and spoke extensively about. Many also have noted how Sergio Oliva was at his best after going to Florida and training under the tutelage of Jones using his equipment and protocol.
