I don't think of my Teslas as just "cars", it's more advanced consumer electronics; guess that's why I call update info standard practice.
OK so I took a poll of my advanced network-connected consumer electronics...
Provides preview of release info, requires acceptance of update: Mac, iPad, iPhone, and most associated software
Does not preview release info, but requires acceptance of update: Tesla Model S
Does not preview release info, automagically updates: ADT Alarm System, Nest Thermostat, TiVO, Roku, OOMA
Some do, some don't. My only point is this: even for consumer electronics, it is NOT standard to require approval for update, nor to provide advance release notes.
What you are using as a comparator is computers, tablets, smartphones… which I agree provide best practices that Tesla should emulate.
Makes me wonder why they don't… as there's usually some reason for these things (even if we may not agree with it). They're clearly not stupid, so there's something.