The body moves the least in REM sleep, Drogo, since that's when you're in sleep paralysis. For survival purposes, the brain paralyzes the body while dreaming so you don't act them out and wake yourself up constantly.

Spaceexplorer, it's partially the lucidology videos but also Jeff777's tutorial for allowing your body to fall asleep before you do. It's basically the same information.
I don't know the science behind it, but it makes sense to me and the technique works. Drogo wants lucid dreams, so I'm telling him what has worked for me based on his current situation.
If it's all a bunch of nonsense, that's fine. But at least it works.
I'll take a look at the link you posted anyways.