So if they detect a trend early enough, they implement it as first-party feature, dry out the existing competitors while restricting new competitors to enter based on the App Store Review...
Apple isn’t using that rule to take down alternate weather apps, despite them having their own native weather app. There’s still plenty of QR code scanning apps, despite that being built into default camera app.
I'm fairly sure "Only high quality apps should be available to users" was said more than once when the Apple AppStore first launched (together with the second or third iPhone I think?). Apple isn't really into the whole "users can choose what's best" thing, which once you understand this, a lot of their choices become understandable (albeit shitty none the less).
"Apps that copy basic iPhone or iPad functionality (including but not limited to its UI, gestures, core features) will be rejected unless the app provides a clearly different purpose or adds unique functionality."
Note the "basic" line. And there are plenty of Photos, Notes, Streaming etc apps so not seeing where this is being used to exclude competitors.