It's pretty clear that's the case. Watches are being assigned to orders only once they reach distribution centres in their respective countries. If they were being assigned from the point of origin, before being shipping out all over the world, we'd all have been charged before they event left China, and receive tracking information then.
What's happened at launch, is Apple has allocated inventory in local distribution locations, and begun fulfilling those orders based on the relative order location.
This is probably why we're seeing people who ordered the same sku in different regions getting their units before others who ordered earlier.
Apple must have been stockpiling inventory at these hubs before the pre-order date, only to find afterwards, they stocked too many of the low demand versions, and not enough of the high demand ones, like the Space Grey Sport. I don't think they ever expected the SGS to be so popular, given they only had it with a single freaking band colour.
I choose this for better wear and tear. I've found that black holds up better then the other lighter colors would. The iPad cover light blue taught me that.