I know a guy who got an A+ in Physical Chemistry at an elite university, and never went to class. He needed the spare time to practice with his grunge band. He told me he spent 24 hours non-stop going through the textbook with the help of some borrowed Adderal.
I suspect he missed a lot of interesting stuff, but he got the competency.
There are plenty of reasons for "seat time" in many areas of study, but certainly not in all. For example, there really are no valid criteria (in my view) for competency in Art History, or in history for that matter.
Here's the idea: Hacking Higher Ed With Competency-Based Education
Related, competency exams may be racially-biased via disparate impact. Here's that whole story, from Bill McMorris: How the Supreme Court Created the Student Loan Bubble - It all starts with Griggs v. Duke Power Co.