The title is clickbait, they're not specifically adding Apple Pay (9to5Google did the same thing with the title 'Walmart finally supporting in-store tap to pay with Google Pay').

They're finally accepting all tap-to-pay payments, regardless of provider: https://news.ycombinator.com/item?id=49388570

It's a big deal that Walmart is willing to concede on this, as they have been avoiding it to gather more customer data via payment methods that don't use tokenization and are less private (fixed PAN cards, Walmart Pay app). The interesting question is: why now?