What part of controlling your impulses in order "to not be pieces of shit" "doesn't make sense"?
I gave the accepted definition of willpower above. The author trying to redefine the term doesn't make it so.
It's like the author trying to say that endurance is the same as free will, because free will can dictate whether or not you train it.
There is the understanding that people are just the result of their genes and environment - this is common sense. Then there is trying to say that willpower doesn't exist at all - it does, and it's medically defined.