The problem with statements like this is that they only ever seem to be made by narcissists who thinks work is only those efforts that directly benefit them. The end of my "work day" is when I start my other job of working for myself. I manage my home, I take care of my garden, I put effort into maintaining or improving my physical and mental well being, I foster and build the relationships in my life that I care about, etc. All of that is work, it's just work that I do for myself and don't get a paycheck for.
Just because he is an idiot who never worked a day in his life and so doesn't know that your productivity goes down significantly without relaxation that doesn't mean that anyone should listen to that drivel.
These people, like Musk, think laying on a couch with a pen in your hand pondering about random shit to be hard work. That's where they come up with this kind of BS. That and being from a higher cast and never having worked a single honest day in his life and making a fortune out of corruption and networking.