Earlier quoted context omitted.
The Apple FAQ itself answers the second side of this. If a browser can add PWA, they can claim they’re installing an app, and it would not be clear to a user that they have a web app, not an isolated app. Now, none of these pseudo apps are guaranteed to be sandboxed from each other but the user cannot differentiate between apps that do provide security.
> Now, none of these pseudo apps are guaranteed to be sandboxed from each other... Except they are! Any browser worth their salt have been doing isolation since the dawn of time. Or do you really think bing.com can manipulate google.com cookies and storage?
Yes, a good browser does. But you’re still leaving it up to each individual implementation, and the DMA rules that Apple cannot judge accordingly.