Earlier quoted context omitted.
Given that students are almost always graded on how well they do on assignments/exams rather than how long they studied, your strong-man competition analogy doesn't make much sense.
You're implying that grades are an objective metric of value. This is often false, because the metrics for grading are oriented around what's easily testable , rather than what's actually a sign of good work. Kind of like hours spent in a gym, actually.
It's like if we wanted to test someone's ability to run a mile but had no way to measure time. We'd still test them to see if they could complete it, and if they can't, well they certainly can't do it quickly. But anyone competent can most certainly pass that basic test.
Grades aren't an opportunity to show off, they're an opportunity to express basic competence.