I know, there are plenty of cases (and this is why we should defend our rights and support associations like https://noyb.eu/ in my opinion), but I would object that having an app, running on an always-connected smartphone, which register and share data, poses a potential higher risk than an embedded device with a much smaller task that is tested and validated before being sold on the market. There is almost no data record in this case, thus a leak would have a minimal impact, while a backdoored/tampered/non-compliant hardware would still be problematic, but less likely (hopefully).

Your previous car could have had a non-compliant implementation, but it could be that the system run a passive network scanning from time to time, without trying any connection, just because it would be way faster to connect to a network and send a message if there is an up-to-date list of the compatible available operators. Having a better understanding about the specifics of the various implementation would be interesting. The devil is in the details :)

To connect to cellular (2G/3G/4G/5G), you have to listen for a beacon from a base station. If you don't hear a beacon strong enough, you aren't even allowed to try to connect (as it involves transmitting a connection request).