Mentzer was a Jones devotee but clearly got a little too obsessed with the philosophical idealism side of things, latching onto the principle of what made jones different from everyone else (more intensity, less duration and frequency) and becoming derviative of that until you get to his final product in which Mentzer was advocating as little as one session every 10 or 14 days?
Jones never went that far, in fact the standard AJ "protocol" was a full body training session 3 x a week. Jones after about 20 years of continuous research (I think a lot of people are unaware or don't appreciate the work that came out of the nautilus facility... nobody was, or has, since, devoted as much money to bodybuilding research as Jones did) stated that they found some people got better results out of only twice a week, and some individuals still had to be limited to once a week. Jones was not ignorant of individual variability. Jones was also not ignorant of genetic suitability to tasks, and said something to the effect of "most people involved in the earnest pursuit of bodybuilding are completely wasting their time, deluded into believing they have a hope in hell of competing with the absolute genetic freaks that are placing on stage today"
Mentzer's work is admirable in being one of the few literary treatises on the theory of hypertrophy... its just that his conclusions were self-evidently wrong. HIT in general, however, it must be said, will always get an unfair rap because it is simply hard work. I remember reading the study conducted at west point using Jone's training methods pitted against Dr Cooper's then standard military prescription of long distance jogging and calisthenics. The HIT group ended up making gargantuan improvements in all measures of fitness, including cardiovascular, and blew the cooper group out of the water. That was in the 70s. It was never adopted. Well the army continued in the fashion of lots of jogging and lots of calisthenics up until the 00s when the special operations groups discovered that weight training was reducing their rates of muscular and joint injuries in the field as well as improving their capacity to perform in field conditions. Jones probably wouldve been chortling in the grave, finally vindicated.
Point being: even if something is demonstrably superior, if it is too hard, people will come up with excuses so profoundly complex and contrived you could scarcely believe it.