I still don't get the difference between high profile "partners" who have "signed up to Apple Pay", and any old retailer who accepts NFC payments. Surely there's no difference; is it just Apple marketing spin?
No difference. The partners get advertising from Apple and the partners will market Apple Pay to their customers (i.e. marketing spin).
Pay is not the amount of marketing being done, but that only one of these implementations is more convenient than just using a credit card. Hence G Wallet is only used by a handful of nerds while