> Whether a user is in Safari, Safari View Controller, or another browser on iPhone or iPad, when they tap “Add to Home Screen” and create a web app, the cookies are copied over, including the information about login state. This will only work if the authentication state is stored within cookies. No other kind of local storage is copied over.

> After a user adds a web app to the Home Screen or Dock, no other website data is shared, which is great for privacy.

So an offline-first app will not work. A user has to login if they want to see the same data when they open a web app from the home screen and when they open the same web app from the browser, and the data has to be synced in the cloud to make that work. Great for privacy.