Just read what I said again. Mrs Spudger does this for a living. She knows what she’s talking about. The phone doesn’t have to be connected to the public internet. It can just be connected to a private wi-fi network for this purpose.
Phones like this are very tightly locked down. This is not the iPhone you may be used to. The management software even has its own private Apps Store. The user can’t just add or remove random apps from the public App Store. The device manager can also prevent any deletion of content.
These things aren’t left to chance, especially when we’re talking about the highest office in the land.