I was surprised also when I requested my medical forms and found out that I had been diagnosed as bipolar 1 instead of 2. I didn't consider mine that severe either. I was hospitalized but was initially for being suicidal. I think the key is the mixed episodes. I have had quite a few of those. It seems a lot medical sites list mixed episodes as usually a diagnosis of bipolar 1 over 2; and it could be considered more severe because the possibility of suicide can be higher. The depression is there but so is the energy to do something about it.

Here are some sites that include information about mixed episodes:
webmd.com/bipolar-disorder/guide/mixed-bipolar-disorder
nimh.nih.gov/health/publications/bipolar-disorder/index.shtml
psychcentral.com/lib/the-two-types-of-bipolar-disorder/000612helpguide.org
mental/bipolar_disorder_symptoms_treatment.htm
bipolarmixedstates.com/bipolarmixedstates.html