Here's another real deal old school guy. He has many videos out and here's one if you're an older/old guy getting back in shape.
Another one about over training
Another one about over training
Too much volume and frequency for me, although I did volume in that neighborhood until my mid-40s. Wouldn't dream of doing it now unless I was just going through the motions. (Thing is, I wonder if I even needed it then. Probably not.) Also, he said something about taking 30-45 seconds or so between sets. Even when I was in my 20s and 30s I never took such short breaks, let alone now (drop sets excepted).Here's another real deal old school guy. He has many videos out and here's one if you're an older/old guy getting back in shape.
Another one about over training

Where is the evidence against it?The assumption though is must be recovered before next workout.
Where is the evidence for this?
Yeah, but are they in it for the long haul, or just the next competition and then they take time off for full and proper recovery? Not a rhetorical question.I think its also important to consider what your goals are. If you train not fully recovered this will increase your recovery capacity and also your threshold for how much volume you can tolerate without burning out. Our bodies are not as fragile as some fitness people will have you believe. There was a study I read where they tested people with squats every day and these were trained athletes. They were extremely fatigued and mentally drained but they were still able to set P.R's when push came to shove.
https://shreddedbyscience.com/study-spotlight-squat-every-day-study/
There was another study where they took a Norwegian power lifting team and had kept volume the same but some did it in 1 or 2 sessions per week and others in 4-5 and the people who had more frequency had far better results. I dont have the link for this but you can find it.
The evidence against it is the overwhelming majority of people in the gym who are going multiple times per week and still making gains. What do you think the breakdown is between those that are in the gym 3-5 times weekly as opposed to those that are in the gym once every 7-10 days? I asking and I don't actually know, but based on casual observation the majority of people are in the gym a hell of a lot more than you're suggesting. Not that isn't working for you, obviously it is, but mainstream, I just ain't seeing it. And again, these more frequent gym goers are making gains.Where is the evidence against it?
If you're breaking down the muscle again before it has a chance to recover, let alone overcompensate, what is the expectation?