I am still thinking this is mislabeling. This is like when British Airways charges a USD card in USD even though the processing is done overseas. The evil thing about this is even if you're using the US website and all prices are quoted in USD natively, you still get hit with a foreign transaction fee if the card has one.

I think a similar thing was happening here where people were getting double points on GBP-denominated foreign spend. While I did read some of the comments on that linked article, I didn't see any glaring examples of DCC having occurred over AmEx's network.