Is there any information about precisely what vehicle telemetry they capture and retain?

I know the laws are far from perfect, but isn't there some legislation compelling them to disclose what they collect?

What specifically would be the most relevant law/regulation? (If it varies by geography, pick any major market, eg. California, that is big enough to impact their engineering design and the content of published material). You mentioned they're cagey, and my aim is to examine if there's a gap between what they're supposed to disclose and what they do, which could be rectified by litigation. Eg. If they just say "vehicle telemetry" that doesn't tell you much, and I'd happily contribute to an EFF effort to get them to elaborate.

Alternatively someone who works close to this code could provide some examples of what a "typical" smartphone OS platform collects these days.

GDPR should work to get a copy of the data, also it would only be allowed to be collected with explicit permission -- I'm assuming that data about your car is PII about you.

Generally speaking the author seems to wave a bunch of conspiracies around without the evidence to support it, or frankly, much technical knowledge.

The author seems unaware that in iOS you can uncheck nearly every single location usage the OS and Apple Apps themselves collect.

On iOS not only can you shut off things like traffic reporting while using Maps and cellular/WiFI/Bluetooth data collection...unlike Google, Apple will let you use those services without requiring you contribute to them.