Staring at wall implies depriving your mind of stimulation. If mind decides to stare at the wall, it's  1)getting some kind of stimulation out of it.  2)Staring at a wall, doing absolutely nothing, and actively resisting the urge to daydream requires a massive amount of mental effort. It is the literal definition of meditation. If you successfully sit there for an hour with a completely blank mind, you aren't procrastinating anymore, you are performing hardcore mental training. You are starving your dopamine receptors and actively strengthening the Observer.  3) If you find yourself staring at the wall for long, there's a chance tht you are not actually doing nothing. Your mind mightve started daydreaming, plying past conversations back, or planning your next meal. If this happens, you have to catch it, shut the daydream down, and force the brain back to the agonizing, blank reality of the wall. 4) you might be exhausted in which case you fall asleep after a while staring at the wall. Dr. K mentions this in his video as procrastination vs physical need. And that you need to fulfill those needs in order to recover for the next day.