Specifically, I think they should minimally penalize students who know the material and could apply it professionally, but don't do well on exams in general. Otherwise GPA isn't a useful metric for employers* (and I don't know who else would it be a metric for), because the best students are the best test-takers, not the best employees.

So, maybe not a baseline. The exam could have some difficult knowledge-based questions, as long as that "knowledge" when memorized would make the student a better professional; or if the exam is open-book, it can have knowledge that would be difficult to search for. It shouldn't require students to memorize obscure things that are unlikely to be used professionally (e.g. unimportant dates for history, or complex formulas for math that one would look up or reference by name), because then you're prioritizing students who handle rare edge-cases over those who probably accomplish more amortized.

* "Employer" and "professional" also including "PI" and "academic"