"If you're not drawing 24/7, you aren't working hard enough"

[ReneAigner]

 But I think it is pretty obvious that if the same person works 12-14 hours a day instead of 5-8, they will progress much faster. 

I don't think that's obvious at all. There's only so much you can learn in a day and only so much concentration you can muster. 

There is a lot of  groupthink going on in certain circles regarding how all that matters is the time you put in. I think it's delusional to a degree. Of course, getting better takes time and practice. But there are other factors to this as well, e.g. how "talented" a person is (as in how fast/efficiently they learn), how open they are to new ideas, what the quality of their learning resources is like, etc. etc.

Take Noah Bradley who has always said that he worked less than most of his classmates in artschool, and yet I'd say he's done rather well for himself.