I'm mostly a law professor these days. When final-exam time rolls around (as in, this week), I raise my eyebrows when I'm sent the list of students who get 50% extra time. I wouldn't presume to judge the propriety of any given student's accommodation. But many of the accommodated students seem to have done just fine in class discussions during the semester.

FTA: "Unnecessary accommodations are a two-front form of cheating—they give you an unjust leg-up on your fellow students, but they also allow you to cheat yourself out of genuine intellectual growth."

FWIW, consider that some of these students may need the accommodation specifically because of the pressure of the final exam. Many mental health disabilities will become worse with stress. A low stress environment and a high stress final exam could trigger entirely different symptoms.

For example, I have OCD (real, diagnosed, not the bs "omg im so ocddddd"). I have extra time accommodations because I have to spend time dealing with my OCD symptoms. With treatment, they tend to fade into the background. They re-emerge only in high stress situations. I would seem like a perfectly normal student in class, but then clearly start struggling with these symptoms if you watched me take an exam. Consider, many other students you teach may have these same experiences.