There are many anittrust arguments that can be taken up against Apple, but I don't see how this is one of them. They're adding a feature to add a QR/bar code to the wallet app. It's a very minor feature.

As for sherlocking, this is such a minor use case that I'm not sure why anyone (minus maybe the initial app developers) would be upset. As a user, I need one less app to do something (that I should've been able to do for years). It's not like they're stripping an ability away from developers to hide it behind their own gates.