I agree with Merlin: you do not need to meet 100% of the criteria for mania (or even hypomania) in order to be considered (hypo)manic. I know I don't remember the criteria fully, but I think there are 7 or 8 "bullet points" and you only need to meet 3 of those to be considered (hypo)manic (or 4 bullet points if your mood is only irritable).

I know personally that I have slept normal amounts when hypomanic, especially while on Seroquel. But even 6-7 hours of sleep for me can be indicative of hypomania, since I normally get 10 hrs. So for me, decreased need for sleep is relative. Lots of people tend to get 4 ish hrs of sleep when hypomanic, but I only go that low when I am full blown manic. But in the past, I did go without sleep for 3 days while manic on adderall xr. However, I blame the medication for such drastic changes in sleep.