You would probably want to download the latest update rather than using the old version from the system image, but that's correct. Though IIRC the Facebook "app" the article complains is just a minimal placeholder, with the real app downloaded from the Play Store.

There are some built-in iOS apps that can't be deleted at all, such as Photos. For those that can be "deleted" Apple says users can restore them by downloading the app from the App Store.

But if a user deletes all the built-in apps that can be deleted, are they restored if the iOS device is reset? I would assume so, since wiping a phone is recommended before reselling it and a new user may be confused if default apps are missing, though I don't want to wipe my device just to confirm.