My main disagreement with this type of quote is how do you account for R&D? You have to try things out, not all of them work out, you throw things away, things don't work out as expected. If you're in a true startup, money is tight, deadlines are agressive, you have to put in the time.
If you ask me, R&D on a tight budget and timeline is the worst time to be overworked and exhausted, as it renders you less creative, and far more prone to make mistakes.
Obviously it's a cost-benefit curve, but the research shows the benefits don't outweigh the costs beyond about 60 hours per week.