Wow, I've had the complete opposite experience. In most/all stores I deal with regularly, you can swipe your card at any time while they're scanning your stuff. You can do the same thing with the watch. I've been able to get away with using it in countries where it wasn't officially supported yet, as well, since it's just NFC and no one has explicitly blocked Apple Pay there (sadly not the same in the US).
Results may vary.