I’d guess the reason would be different, I think that a person that gets bothered by music repetition would not work as a music teacher.
You might avoid moonlight sonta, but then it’s 500 servings of fur elise.
Or they've learned through their experience they simply don't like the kind of person who insists on learning the one song they like, and can't teach them well, so it's a good filter.
But hey, not every teacher is for every student and vice-versa; and that's okay.
a major rule should instead be: "choose the song you love and let's learn it" -- tells me a lot more about the kind of teaching they do than off the bat shooting down songs. sounds obnoxious. teachers can do whatever they want ofc. doesn't make them good teachers
I think people can be allowed one song they are tired of.