I see that here is some fundamental confusion about App IDs.
So note the following:
App ID should be unique per page!
Otherwise if keeping all the same app id, you risk in loosing all meta data when renaming the app id.
So each layout page, content page etc, should ideally have its own unique app id.
Content pages without app id, will inherit the meta data from the layout page.
The whole purpose of having App IDs is that you create a metadata store per page that stays the same even when the page is renamed.