Are you saying you're against intermittent fasting (ie, eating in a 1-6 hour window)? A longer fast would/should only be done ~1x/year.True, but has fasting been shown in humans to extend lifespan. Acute short term fasting has been shown to solve health issues, but is regular fasting necessary and/or beneficial? Generally not.
It wasn't meant to be full of assumptions, it's merely based on a large number of anecdotal evidence (as there are no studies on that protocol). Extreme dieting protocols, including fasting, have been shown to be very unsuccessful in the long term. Most people would find fasting for 5 days very tough, not even to mention doing it repeatitively with minimal breaks. Have you personally done this spesific protocol or know of people who did it with great success and maintained that success in the long run (without using anabolics or sarms etc.)?
You said: "Seems to be the best strategy for long term fat loss". I'm sure if it was so successful people would be all over it. I'm not saying it hasn't worked for anyone... it probably has, but I wouldn't bet on it having a positive effect long-term.
Yes, training does encourage muscle mass retention, but during a fast, it might not mean anything. Your body needs glucose from somewhere and if it's not entirely going to come from muscle, it's going to come from organs and other tissue that contain amino acids. Furthermore, training in a fasted state significantly increases the cortisol to testosterone ratio, and given that you won't be eating afterwards it will keep that ratio sky high for days. Ketones might spare protein to a degree but ketones take many days to rise to a meaningful level. Hence, people lose the most amount of muscle in short term fasts. But even if someone eventually reaches their goal weight, they'll be "skinny fat" due to significant muscle loss.
I've done a lot of different kinds of fasts before and some had good short-term effects but non of them were sustainable and non of them came without the cost of losing a bit to a lot of muscle mass. I haven't done an exact fast like this before but I'm sure I wouldn't want to try it either.