Isn't that what you expect if it does not yet have storage permission?
Why does that bother you.

Also you don't have to re-image the phone, I believe it should be enough to remove permission in settings.

Since pages are saved to app-private storage, we don't actually need storage permission, right?

THis works as intended. Both file downloads and page downloads ask for storage permission to indicate they are going to use (permanently until user deletes files) some storage on the device... THis is in contrast to automatic (cache-like) mechanisms that have automatic storage management so they don't need to ask.