With 30sec you only have time to outline, make them stickfigury or maybe capture a single detail or so you find interesting, try longer formats ones your warmed up.
Personally I like the session classmode 30min as warmup!
The way it progresses from short to longer gestures loosen your drawing in the beguining and progresses into having time for more details and focus on proportions. Give it a try!
Doing longer studies helps you make your shorter gestures better too if you ask me.
My 30sec are kinda stickfigurey, 1min I try to block them out kind like in your linked gestures and the 5-10min I try to get down as much as possible using the previous stick/block technique and detailing onto that
