> But isn't the promise of Apple Pay that you never expose your real credit card # to the merchant? So they can't track you? I know Walmart in Canada really resisted Apple Pay for a few years because it would mean no more ability to track people by their payment methods.

Yes, this is exactly what Walmart does in the US since they still don't accept Apple Pay/Google Pay. When I go in and make a purchase using my credit or debit card, they'll associate it with my Walmart account and it'll show up as a "recent order" in the Walmart app because I have the same card saved there for ordering groceries online. They use those in-store purchases to recommend things to add to my grocery orders all the time.