In the US a lot of terminals that technically could support Apple Pay because they use NFC (and have the logo you mention) have explicitly disabled Apple Pay su

In the US a lot of terminals that technically could support Apple Pay because they use NFC (and have the logo you mention) have explicitly disabled Apple Pay support. So the scanner 'sees' the watch and kinda starts the transaction, then fails later because it's "not supported yet". Because they have a vested interest in a competing product.