How strange. I've never seen this before. And I actually have multiple stainless Apple Watch models for comparison, and none of them have what your photograph indicates. Unless there something Apple is doing differently or they changed something in the manufacturing process, I have no idea why it would look the way it does. As small as that whole is, it's actually annoying to see the white versus having it being blacked out or with mesh intact.
If Follow up with Apple on this, please let us know what you find out.
It's ridiculous- both watches were manufactured in 2015 according to the chipmunk serial number website.