I think a technique like this is great to really understand how unproductive we are with things and optimize to weed out the unnecessary. But, I'm skeptical about how such thinking can help with creative endeavors like writing, painting etc.

IOTW, use this technique to not let junk-habits creep in. but thinking that this can be used to improve productivity is meh, to me.

I can see a good followup here: which is identify that if we don't organize activities, we will have a lot of 10 min windows, that tempt us to do junk things, like browsing, watching tv etc. but, if we can get the time management compressed to have like lesser gaps, we could use solid hours to do more immersive things.