.
It's a good compromise, I guess. Those factors share similar qualities, but while in jhana they are much stronger, undisturbed and purer - so they are jhana factors now, not just mental factors.
I just defended the notion, that similiar mental factors appear before the actual jhana...or even lead, or show the way to it...but they don't have to be exactly the same thing, as their greater peers, present in the jhana.
It's like a relation between two different fires.