I don’t think of grit as work ethic necessarily. It’s resilience. A lot of kids have fabulous work ethic and the grades to prove it. Grit is different. It’s the ability to move forward when being knocked down and to remain focused on a goal. A lot of top HS students find they don’t actually have that once they do face adversity.
Part of the problem with measuring grit in the college app process is you often can’t see it, either in well-positioned students that look good on paper or embattled students who claim it on paper. There have to be people trying to measure it, though. And it is learned. I was one of the top students in my class as a kid but I did not learn resilience either on an academic level or personal level. My classmates who struggled more in school have -predictably - been way more successful in their careers than I have. The concept of grittiness is often misapplied but I do think it’s a valuable concept.