It was also switched off, seemingly, right around the usual 10am Cupertino release time (which was probably when it was accidentally switched on yesterday, too, at the same time as the latest beta releases - it just wouldn’t have appeared until overnight when Wallet updates itself).
I had it only on my Visa cards, despite having several Mastercards and an Amex in Wallet.
All the reports today that I’ve seen on the feature (except yours) only referenced Visa too. However, Apple Card is Mastercard and it does seem to be a version of the feature mentioned in the 9to5mac article, so it’s not surprising that Mastercard can use it too.
It’s just surprising that yours is the only Mastercard report I’ve seen!