Indeed, gestures are more about feeling the flow and putting that on paper as fast as possible. It also helps with memorizing poses for future use (for example if your goal is ever figure drawing from imagination) or just to loosen up and make sure your figures aren't stiff when drawing even if from reference.
When doing more detailed figures and making sure proportions are in check etc, you are practicing more hand eye coordination and measuring
When focusing on 3D building blocks you are forcing your mind (hopefully) to really see the 3D shapes on purpose, to really visualize and simplify things into these forms and become more fluent in being able to later on manipulate them and "sculpt" anything you want.
The more I advance the more important all three seem to my beginner mind. The combination of all three ways of seeing it is really the best way to go and it's all essential stuff for drawing figures XD it all sounds so redundant when I speak of these things when they are literally called fundamentals, but yeah, yay for art epiphanies
cheers!
Also, I started doing gestures way slower than suggested, I just wasn't capable of 30s gestures XD
