> They are both very cagey with how they talk about this (or don't).

No, not really - at least not apple. They are very clear on what CarPlay’s privacy stance is, and they’ve got privacy white papers on pretty much everything:

Eg. https://www.apple.com/privacy/docs/Location_Services_White_P...

Again, at least on the apple front this comes off as a ton of “stated without evidence “