Do you have a source for this?

After looking this up, I found an article in a medical journal that says something very different. Mixed episodes are no longer held to a time constraint, unless they suddenly changed it back???? But I cant find that.

"In the preceding DSM-IV-TR, mixed episode was defined in the context of BD type I as an occurrence typified by the concurrent presence of full manic and depressive phenomena in an individual for at least seven days. This narrow definition was radically modified in DSM-5, with its redefinition that the presence of only three symptoms of opposite mood polarity was sufficient to qualify for the specifier “with mixed features”

I can't afford the DSM - 5, otherwise I would look it up myself.