Eczema is a skin condition which happens to some people, it’s not something that happens in most people. But we can see evidence of varying degrees of severity of skin damage due to eczema. This condition can happen for any number of reasons, immunological, endocrinological, or some combination of factors. There are different types of eczema, but for ease for conversation with anyone other than a doctor, you just say you have eczema.
Same for mental conditions, they have their underlying causes, and some representative characteristics we found on average and grouped them as classes for ease of diagnosis and treatment.
I understand the folly of mischaracterizing, so it doesn’t make sense for researchers or medical professionals to not care about the categorical distinctions.
However, as far as the normal public is concerned, someone’s problem is their problem, and they don’t owe you a detailed explanation of their condition, or a doctors note because you’ve been socially offended (I understand maybe that’s not the point in either of your posts, but I thought I should say it now that it occurred to me in the flow of this post).