This is stupid advice with sole purpose of keeping students engaged in publishing incremental research. So that no one questions vanity metrics like H-index and the ridiculous condition of academic research.

As a PhD student the real secret strategy is to ignore academia, work only on very high impact projects ( with potential of becoming startups or revolutionizing the field), intern with production teams (in core areas) at great companies. And enjoy lack of 9 to 5 scheduled life.

The deep work in less hours is meaningless if the work itself is merely publishing "Minimum Publishable Units" couple of times every year. It's just fast track to mediocrity.

Though I agree that not all environments are hospitable to risk taking. But then dropping out is a better deal.