"...Relying on an app to handle service is the worst idea in the world..."
Its a personal preference. For me, so many benefits to Tesla app-based service. #1 I don't have time to waste taking a phone call on the service advisor's schedule. With the Tesla app, I can communicate on my schedule with the service team. #2 The ability to schedule service and provide lots of details. #3 All prior service appointment history is in the app, and within moments get full service history, from app-based conversations with the service tech, to service invoice.
I can't see buying a car where I have paper (!) receipts to keep track of for service history, have to play "phone tag" with a service team member to have a conversation, or not be able to provide precise details of a maintenance concern.
My service history includes trim fix after delivery (10/2018), v2.5 to 3.0 computer upgrade (10/2020), interior camera fix (2 visits--2022), and alignment (6/2022) immediately after installing new tires. Each service visit was easy. Bonus was being at a service center and seeing a Roadster and talking with the regional lead mechanic for Roadsters--super friendly.