I know the experience you're describing, in the half-sleep state. If you ask me, it's kind of like a spectrum of awake--->asleep. Consciousness can be maintained or re-gained at any point on the spectrum. On the lightest end, there's active imagination, followed by audio hynogogic sensations, visual hynogogic imagery, and then dreaming. Of course, what one experiences when can vary person to person.

I love active imagination. This is where we can lay down, close our eyes, and imagine any kind of scenario. As trance deepens, we may experience parts of the imagination are not created by us. Instead, it seems to be a "blend" of our imagination and dream material (which I would say is coming from "source", but will leave that open to your own interpretation).

So is there a difference between states? Yes. I would argue that there is a distinct and definable difference (no blurry lines) between any pre-dream state of hypnagogia or active imagination and a true dream state (lucid or otherwise). This is evidenced when we have a WILD (wake induced lucid dream). If you go through the WILD process, it's clear when you have "lift off". Before that though, it's definitely a blurry line when dealing with active imagination, hypnagogia, trance, etc.