Feast & Famine is alive and kicking in even the most affluent of countries, not to mention the rest of the world, for most of us genetically speaking it was likely a regular experience 3-4 generations back so I don't think we've evolved away that far yet, and that adaptation is too important to throw away on the basis of 3-4 glutonous generations.
As for the muscle issue, that is applying artificial conditional rules to optimal health, significant muscle mass may under specific circumstances have endowed an evolutionary advantage, but in most cases would have been a disadvantage that required extra maintenance and may well have constricted an individuals all round performance.
When you apply conditional rulings such as this or <5% body fat for muscular exposure, marathon running, aesthetic criteria body weight and shape, longevity etc. means that optimal health is compromised and is one of the reasons these discussions never go anywhere, because there always seems to be a hidden factor people don't reveal.
It is simply imposssible to drive your body down to <5% body fat and then expect it to perform well under IF conditions, there's no give there, the body is already at the doorway to starvation, so low carb & IF will be a dismal failure for these people, that doesn't mean that there is anything wrong with low carb or IF though.
Hence dietary and metabolic response will be similar within a similar subgroup, but not within others, I'm not quite sure exactly where I place myself but am aiming somwhere in the mid to upper ranges across the board, but likely have unidentified factors that may be skewing my own approach so still looking around.