The background-permission answer is the mechanism I was missing. I had written the phone problems up as four separate quirks and they are one thing wearing four hats.
Also fair on recommending version control too broadly, I have done that to someone and it did go exactly as described, on a train, with a merge conflict.
Adjusting my own summary: if the phone is a writing device, the paid service is buying you a fight with the operating system that you do not want to have. That is a clearer reason than "convenience".