Your instructor would be wrong to just let this happen AND reduce your grade as a result. I don’t know the answer. Stuttering is a disability. You don’t dock someone with a disability because they’re physiologically unable to complete a task because of that disability. It’s like docking a blind person 2 grades in class because they can’t read the assignment. No, you find a solution to allow that person to achieve the goal a different way. 40 year old me would pitch a bitch, 20 year old me would probably just shut up and take it... :(