Yeah, I'm sure Google wants to keep that side, the whole set of algorithms and procedures, as tightly-held as possible.
This would hose their methods for server load balancing, testing-incorporated-roll-outs, the whole bit, if we all posted the "here's how to get GA right now" threads ;-]
Not that it's just them, Windows, and many others are all staged, and many, many online services do the same with bug fixes, platform improvements, etc, particularly those that can't afford any perceived downtime.
The interesting thing though, is that you'd think they would've used your IMEI or MAC for validating this, in such a way that if you re-enrolled, the match would be more or less instant. This particular algorithm is "odd" in that way, perhaps for reasons we're not considering, or I'm not anyway ;-]
I seem to have (even for my short time on Android now, I'm 9 months from Win Phone, since it's inception), I seem to always be at the front of the queue, for updates and things like the GA enabling.
Only once, when we were moving to 7.1, did I have to wait more than a day, from when I saw the posts, in particular I seem to always get the patches, day-of.
I wonder, perhaps it's because I was on the Nougat beta, but then
@LeoRex's experience doesn't figure (at least for the GA "selection algorithm").
Of course, now that I've said this, I'm sure my next umpteen updates are going to be on the 3+ week schedule, or I'll be stuck in some "non update" loop (I've seen a few here off/on seems like), ugh. ;-]