I think at this point we can assume the Space Gray 42mm is constrained. If like some have said, Apple has a stash of the models they predicted would be most popular already in the states, it doesn't make sense why those that ordered the earliest are slowly getting shipment notifications as planes land from China. If anything the early orders would be getting watches from these "stashes" and those that ordered later would be getting them from China. I think any and all stock is all coming from China and if enough makes it in the next day or so us 42mm space gray people may still get it Friday. I have my doubts though.
Bottom line is I don't think Apple has a magical domestic stock of watches.