I believe it's a much more fundamental difference than just the distinction between ideating and acting.

Many people occasionally experience the transition between "conencted" and "disconnected" states as a sudden jerk or loud noise just at the moment of falling asleep.

Sleep paralysis is another "failure mode" of this mechanism that reveals what's going on. (I'm not sure if there is a reverse to it, i.e. whether sleepwalking could be explained as a drastic fail-open of the same mechanism).

I read a book, just a few weeks ago regarding this specific topic and my explanaition is directly from that book. We do have specific brain areas for this.

This sudden jerk you can read about it here: https://en.wikipedia.org/wiki/Hypnic_jerk and its not scienctificly clear why and how it works, the best assumption is that its a reflex.

You are not disconnecting your brain from anything.