White labels and dubplates in general hearken back to the sound system culture that originated in Jamaica [1]. Mostly a means of getting the newest songs fastest; record something in the morning, press your dubplate that afternoon, play it out that night. The unofficial nature of the recordings makes it easier to hop around copyright stuff and not clear samples, etc. The song Alicia by Mala jumps to mind [2], I don't think it's ever seen a proper release because of the heavy use of Alicia Keys samples.
Again, I don't see how pressing a physical recording is making anything faster. It's a step that's entirely unnecessary if you distribute digitally. It must be more of a tradition, or a desire to mix on turntables, or possibly a way to do a limited/controlled release that is not easy to redistribute widely as a digital media file would be?
Combo of all of those, really. Particularly the exclusivity bit, songs that get pressed like that generally aren't things people are trying to share. For instance, dubplates use acetate and not vinyl, and are really only good for about 50 plays. Lots of exclusives becomes the reason to check out your party vs the one the people a few blocks down are throwing.
He did say this, but maybe it wasn't clear. It's faster because you can skip the meaningless bureaucracy associated with obtaining copyright permission for a tiny run - a lot of dance music samples other music. If you try that with a digital release, it can bite you if it blows up.
1. https://en.wikipedia.org/wiki/Sound_system_%28Jamaican%29 2. https://www.youtube.com/watch?v=zpV7radKuwo