The big problem I have with this advice is that it can’t be scaled up to everbody. If everybody were to follow this advice, we’d have a situation where everbody works 4 extra unpaid hours and nobody stands out. Advice which becomes worse the more people take it. Not good.
Secondly, working more hours might decrease your efficiency in the long run, leading you to finishing less work than if you took the time to rest. If reduces your efficiency by just 10%, you’d already produce less value. While it’s unlikely to get that far by just 4 extra hours, you don’t get the full 26 extra days of productivity.
And if everybody were to follow this advice, always trying to work more than everybody else in order to stand out, we’d soon reach a point where people would produce less.
The advice is basically actively harmful to society.