Being competent (top 20%) and working 3hrs / day is way more productive than a middle performer working 12 hrs / day.
In my personal experience:
I work with people that, in 5 minutes, I can accomplish more than they can in a day. And those people are not stupid / unmotivated.
I also work with people that, in 5 minutes, can accomplish more than I can in a day. I'm not stupid, or unmotivated.
Some people are just more experienced, have better judgement, are smarter etc.
Output is what counts, not time.