The study I have seen claimed that 40-50 hours long term have same output and then it goes down. The studies on game development teams found that crunch raise productivity of short (don't recall if 3 or 6 weeks) and productivity goes down only after. This article does not seem to adress concrete studies nor their results - it just generally theorise about what might be wrong about them without knowing what is on them…
Do you have a citation? The post is mostly to address this constant claims that 40 hours is proven by science and no convincing citations are provided.
I am also writing in the context of self-managing knowledge workers who can manage their own time. I explicitly write that the flexibility we have may mitigate many of the downsides observed in mandated long hours. For example, I do work >40 hours, but I rarely have to wake up with an alarm clock. I can follow the occasional 16 hour day with a 10 hour sleep cycle and stroll into work at lunch time the next day feeling pretty relaxed.