Or they could've just launched it 5/8.
I would bet they considered this. Apple knows people like uniformity. Customers are used to a product announcement + a couple days to preorder + plus another week before they ship.
They Apple Watch had more buffer time than this, but it was close enough to the previous layout that people stayed quiet.
, I would appreciate Apple telling me now so I can buy a color that's available.
Apple will never reveal information like this. Apple will never issue a public statement that they are 'low' on any model. You have to read between the lines.
If it is really an issue, spend some time reading the other threads to find which models are shipping now. Order that model, and return the one you don't want within the 14-day window. (And at this point you should have both watches within that window anyway)