This sounds like an argument against rubrics or ladder requirements in general, not a particular problem with mentorship as a requirement. If you want employee

This sounds like an argument against rubrics or ladder requirements in general, not a particular problem with mentorship as a requirement. If you want employees to mentor others, call it out as a thing to encourage. If you don't do that, people will be less inclined to do it, instead focusing on raw technical impact or whatever. Why call out writing good code as a requirement for advancement if everyone should do it anyway? Well, not everyone values the same things. Making values explicit isn't bad.