If you're going to "practice" guitar, then actually concentrate on what you're doing - don't just have one in your hands and fumble around with it while you're watching TV - focus and you will improve.
...which blends with another maxim I picked up:
There are some guitarists who can truthfully say they've played for 40 years - and it sounds impressive until you find out they've only played the same 9 chords the entire time.
So I can appreciate what the article is kind of pointing out in a lot of words - "Practice makes better" - it's a perfectly reasonable message to put forward. The examples are okay overall. There's a lesson in there about the ceramics class, but it seems like a setup from the beginning - a lot of varibles in the outcome depending on the professor, right? I mean, just letting the non-quantity group sit there and drool or goof off isn't maximizing the actual concept of reaching for perfection.
Oh, and I listened to a 60 minute long tape of Kanye from that prolific period. The end results are really cookie-cutter. He basically found a sample of music that somebody else wrote & recorded, stretched/looped it, added a hip-hop sounding MPC kit line under it, and called it done. It's a strong example of mechanical repetition to hone the tools of a trade (production/sound engineering). Personally I view it as the antithesis of writing original material, but like I said, personal opinion.