FYI this isn't anything new. The networks (at least Visa and MC) have been routing payments to other networks for years, so that their customers don't need a separate integration with each network (or to use a middleman processor who has integrated with each network).
"Visa Checkout currently supports Visa, MasterCard, American Express, and Discover"
So it seems like they're trying to position themselves as a sort of Square competitor?
[1] https://developer.visa.com/products/visa_checkout/thingstokn...