Like maybe there's some insight on time management but after rudimentary time management...it's probably something else.
And yes, it does depend on the activity, but even cold calling customers all day can become too much, or an extra ten hours of calling could make your sixty hours of programming less productive.
I use Timing app to track my digital. I spin up at 11am, get reving by 1pm and don't stop until I pull up to the drive way at 1am or 2am. Monday to Sunday.
There are plenty like me as owner-operators that put in the time/work to get shit done until there are enough rev to hire out.
At the alphabet soup company we worked maybe 11am until 4pm, wrap up to go home on the busses, put in another 1-2 hrs at night time to checkin. But during that 3-5 hrs it's highly focused flow that takes dozens of other supporters and personnel to get to.
The pirates that go flitter about, whether in silicon valley or los angeles, to get production done, show going, or keep it moving, all work however they work.
This person's obviously crushing it.
edit: not actually good for you
That is not to say that there are others who can do many actual productive hours. But usually, at least in my personal experience, when one does that they are sacrificing other aspects of their personal life in the hopes that when they achieve their goals they can then deal with everything else.
In my experience, things don't really work out all that well. Ideally one should find balance in the now.
At my previous company, one of our (somewhat implicit) values was "suffering is not a KPI".
And even though there are times when things are rougher, these should be exceptions, not the rule.
At the same time, working 100 hours per week is the most bullshit business myth of all.
This is usually touted by the type of person who spends a lot of time in meetings or 'catching up on important news', and within industries where people are flat out lying to each other about how much they actually work (management consultants come to mind, and certainly some investor types.)
When you meet these people IRL you realize many of their 100 hours are spend sipping coffee in another part of town while having casual meetings, prior to running some personal errand. While some of this may qualify as 'work', it is not the type of 'work-work' that a naive coder/entrepreneur is pursuing en route to their burn out!