Topic: Why is alexithymia not distinguished as a separate mental disorder?

I've been reading up on alexithymia a lot, as a counsellor suggested that I might have it (and I'm pretty sure she's right), and I read an article that broke everything down really clearly and talked about different approaches to dealing with alexithymia and all of that (I don't have the link unfortunately). The article mentioned two types of alexithymia, one caused solely by abnormalities in neurological structure (specifically the corpus callosum, I think), and a second type that is developed as a sort of coping mechanism, as far as I can tell, that is more responsive to traditional psychotherapy. Also based on my personal experience (she said that I probably had mild depression as well) it feels like the alexithymia, though definitely related to the depression, is separate from the depression. Like it seems like if the depression was fixed I would still have the alexithymia and it would still detract from my life in a whole lot of ways. Based on my personal experience/feelings and based on the fact that studies seem to show that there is a neurological basis for alexithymia why is it not it's own separate disorder? I just want to know what specifically about it makes people categorize it as a personality trait rather than a mental disorder worthy of research into it's own cure/treatment.