I think the metaphor is OK, but in my own experience I think it misses the mark a little bit. From what I have learned, you need to GC because you generate too much garbage; one of the ways that meditation helps is that you simply generate less garbage (less scattered, less thoughts) thus you don't need to GC/sleep/whatever that much.

And why do you generate less garbage? It's because you become better focused (concentration) on whatever you do (which by the way brings mindfullness as a side-effect, not on purpose). With proper concentration, you also become aware of the "dirt" (word that was used in the article from the atlatnic) and will tend to avoid this dirt. This is important, because if you want to get better at something, you must be able to recognize what's wrong. The problem with having these insights is that if you don't have a teacher to help you, you will get stuck at best or regress at worse.

Also there are alot of different meditation techniques, and although they are similar, the devil is in the details. I'm sure this definition is not appliable to every type of meditation, and that's OK.