First of all, “URM” stands for “underrepresented minority.” It simply means people who are in the minority and are underrepresented at elite schools. It’s not confined to race and ethnicity, and at some colleges includes first-generation college students, low-income students, students from disadvantaged rural areas like Appalachia, etc.
Secondly, it’s not really debatable that diverse experiences and perspectives improve teams and contributions - there’s research supporting that. It’s also true that the only function of racial/ethnic minorities is not to make campuses a “dynamic place” for the majority to attend - to be a feature, like the library or the rock climbing wall.