Part of the whole point is the relation to the quote at the start.
In every one of those apps signing up "doesn't work" which goes against the stated goal of ensuring that users can download the app and expect it work. How can it work if you can't even sign into it because you can't sign up for it and they can't even tell you how to.
Except the app was not rejected for failing to meet the standards of the quote. It was rejected for failing to meet the App Store review guidelines.
This whole website is a strawman built against the false claim that you're not allowed to require a login to access your app, which has never actually been true.
Except the policy doesn't create the trend. The Tesla app won't work if you don't own a Tesla. The Wells Fargo app won't work if you don't have a Wells Fargo account. These apps have external requirements by their very nature, the App Store policy does not change that.
You can't sign up for a Wells Fargo online user account without first having a Wells Fargo bank account. Therefore there is an external requirement.
Update: I just double checked. The Wells Fargo Android app and Wells Fargo iOS apps behave identically. You are immediately presented with a login screen upon launch. There is no signup flow inside either app but you can click a link that opens a web browser with a link to the registration page.
Your claim that the App Store policy is responsible for this trend does not hold up, considering the Android version is not subject to the same policy but behaves the exact same way anyway.
Update 2: Checked a few more apps. The Android versions of Github and Fastmail don't allow you to sign up in the app either. You are only presented with a login screen just like the iOS versions.
Fair enough, but it's not like they couldn't provide a more direct signup option in the Android version if they wanted to. The fact that they didn't is telling, IMO.
To circle back to the original point, blaming Apple for the "trend" of not being able to sign up inside of apps is clearly nonsensical.
Part of the whole point is the relation to the quote at the start.
In every one of those apps signing up "doesn't work" which goes against the stated goal of ensuring that users can download the app and expect it work. How can it work if you can't even sign into it because you can't sign up for it and they can't even tell you how to.