I am BP II myself. Like you, I have always been less concerned about the ups.

However the meds for it have really helped prevent both the ups (to my regret) but the crashes that followed as well.

I think if you are on medication that helps you right now (regardless of your diagnosis) that's all that matters. The study of what mental illnesses actually ARE is tricky.

The common consensus is that they are not homogenous (there is variety in how people experience symptoms even with the same diagnosis - as well as some differences in genes involved person by person)

The DSM is a guide but it's not foolproof. It's more important to look at the experiential facts - in regards to what kind of treatment helps, at the end of the day.

Hope this helps