The iOS Overview article contains an outdated statement that the App Store is the only source for downloading apps:
The only source for apps on iOS is Apple’s App Store, which requires an Apple Account to access.
As far as I know (but only in the EU), it is possible to download apps from outside the App Store. Of course, Apple being Apple, they had to make it complicated, but the statement itself is incorrect. I know I can edit it in theory, but I don’t know what to write there tbh.
EDIT: On top of that, I’ve just remembered that it’s possible to remove the App Store app in the EU, so the subtitle “Mandatory App Store” is also theoretically incorrect.