Earlier quoted context omitted.
I love these stories also but I am genuinely curious how you were able to work 8 hours a day on it and also work your regular job. I assume you don't work a full time job, otherwise it seems unhealthy. I put a lot of time into my side projects but that is mostly the whole saturday and sunday, but even then I obviously don't feel so well rested on monday.
The reality is that some people can just do more per day than others. It's very common in academia that many professors spend their entire lifetime in 60-80hr work weeks their entire life. I remember going to conferences,especially the really small ones, the professors and students would spend all day listening to extremely draining lectures; this one particular conference started at 8.30 am, went till 1 pm, you get…
Is that really the reality? As far as I can tell, the reality is quite the opposite -- that sustainable levels of work across all knowledge work industries drop off a cliff past 8 hours a day, and for deep work 4 hours a day. Working on a side project after work possible for short sprints at a time, but somewhat impossible if you have an engaging day job where you are making good forward progress on your career.
On the other hand, if your day job is well paid but rather dull (quite common in tech), working on a side project is a nice way to retain creative and intellectual fulfillment, agency, and ownership in some capacity in one's life -- it can be an artistic outlet and worthwhile in itself. Beyond that, it can be nice transition to a startup. But I think this idea that some people "can just do more per day" makes the fallacy of thinking progress happens a day at a time. When it comes to side projects or new companies in incubation, that's not always the case. Explaining it away with an argument that is biologically untenable seems questionable to me.