>>> Sure some 996er's at a company at say, the senior management level can be worth it since you do actually get more work done.
Working 12 hours/day is actually more productive for management. Most people look at it from a coder/developer perspective, where more hours does not mean more work given how mentally exhausting the task is and how non-linear the gains are.
(I do not make my technical staff work more than 50 hours a week, and have forced many to take time off / stop working X hours in the office.)
But speaking as a founder/President of a company that has 40 employees, and someone who basically does 40 hours a week of management tasks alone before I do any of my "real job," there is no way I can make my schedule efficient enough to do all my work in 40 hours over 5-6 days. It just cannot happen. I've delegated literally everything I can (I've probably overdelegated to be honest), but senior management just tends to have way more dependencies and a full schedule of corporate partnerships, external sales, marketing, HR tasks, advisery services across various departments, and observation of work and meetings and blah blah blah. I have to work 60 hours/week to get my work done and push the ball forward while I mentor my direct reports and train them. (Typically work 4x12, 1x8, 1x4 WFH).
Yes, a technical worker crushing 996 demonstrably sees exponential dropoff (though I think someone working 80 hours a week still gets more done than someone working 40 hours per week, they just don't get 2x done, probably more like 1.2x), but management is a much different scenario.