From doing a set to failure your muscles recover enough to do another rep in less than 5 seconds
Just look at a drop set, go to failure, drop the weight by 5 kilos and you can do another set, hell you can do it without dropping the weight
Are you saying a single set to failure is more intense than a drop set?
You're missing the difference between intensity and endurance. Train how ever you want. I won't put down your methods.
Yes you can fail at say 9 reps rest for 15 seconds then you can get another rep. Once you hit that failure rep addition reps are just killing your compensation adaption.
Yes, fail at 9 reps. Rest 40 seconds and get then fail at 6 reps to failure. Rest another 40 seconds and now fail at 4 reps. That is not productive training.
I won't respond to what every you type in response. You are not changing my mind. Train how every you want. Yes, multiple sets work. So those short intensity training.