Couple of reasons. Higher frequency = more growth. So hitting a muscle group twice per week is ideal. I’ve done 1.5 years on the 3 full body workouts a week, it’s okay but you cannot hit every muscle. Rear delts, middle delts, rotator cuffs, hamstrings, calfs, traps, all tend to get neglected on a full body routine. How can you possibly do decline bench, incline bench, flies, middle delts, rotator cuffs, long head tricep, short head tricep and an over head press and still manage to do an entire back and biceps and leg workout in 3-4 workouts per week? I think that’s putting an unnessesary contraint on your training. My current split is push, pull, legs, rest, repeat (best gains I’ve ever had). This gives each muscle group a few days rest, while still keeping frequency high. Also, total volume is the determiner of muscle growth, some of the best powerlifters in the world squat 7 times a week. There’s a principle in exercise physiology called the repeated bout effect. Basically what this means is the more your train a muscle the quicker you’ll recover from training it. As for diminishing returns if total volume is being increased week by week, and you’re in a slight calorie surplus then your muscles are gonna grow. The minamilist movement is mainly for hobbysists who are pushed for time and don’t care about developing an overall physique. It’s actually great for beginners too. You don’t want to start with too high a training volume, and it’s important to learn how to bench, squat, etc with good form first. For people who have been training 2 years+ does it work? Yeah. Is it optimal? I don’t think so.
