On some vehicles, you can apparently disable it.

Here's what one guy found works on a 2023 Corolla, where it's getting increasingly-more-of-a-pain-in-the-ass than in earlier models:

https://www.bitchute.com/video/epzioGDOdTeo/

Apparently, it used to be possible to just pull a fuse out of the user-accessible fuse panel in prior years, but that got moved to some internal-to-the-dash panel that's hard to get at.

It also apparently disables the microphone (which you may or may not want disabled) and the front driver's side speaker unless you also run wire leads bypassing the DCM.

I'd also add that I don't know for sure what any other impact is. I'd imagine that it voids your warranty. I don't know if the car manufacturer relies on this communication mechanism to push out firmware updates for the car, but if so, I suppose that one might not get firmware updates.

I also don't know whether the vehicle maintains local logs, even if it's not uploading them, so I'd guess that someone who can get physical access to the car might be able to get ahold of data that might have been sent to the manufacturer via the cell network. I don't know whether part of the maintenance process might also involve uploading logged data to the manufacturer; I could imagine that being the case.

Apparently some older Hyundais disable themselves, because they can't speak newer cell phone protocols, and those older cell towers are going offline, which causes the connectivity to be severed.

https://owners.hyundaiusa.com/us/en/resources/blue-link/2g-3g-wireless-service-update

EDIT: Note that even aside from the telemetry, one point that a number of people brought up when I was reading about this is that apparently car tire pressure systems also do surprisingly-long-range radio broadcasts (i.e. they really only need to go from the tire to the rest of the car, but can be picked up miles away) with apparently a unique ID, so while it's not phoning logged data home, if someone has a radio listening for it, they can detect and log unique identifiers of cars within range. If you have enough people with receivers participating in a network (the way people have with AIS for ships and ADS-B for aircraft), then you can build a map of where vehicles travel, particularly if you can correlate signal strength across multiple receivers.

I'd imagine that you could cross-correlate any unique IDs being broadcast over the radio with license plate numbers and an image of the vehicle if you stick a camera somewhere aimed at a high-volume road, like an interstate highway. A single encounter probably isn't enough to link license plates or the like -- there will be multiple vehicles in broadcast range. However, once a vehicle has passed such readers twice, that's probably enough information to uniquely identify the vehicle, since it'd be unlikely to have two different vehicles both in range of the receiver at the same time. Any additional encounters with just add confidence. I don't think that it'd take a great many such readers to get a national database built up pretty quickly.

considers

I suppose that if you can correlate that with personal cell phone IMEIs -- cell phones broadcast unique identifiers in the clear that are linked to the phone, not just to the SIM -- that you could also do a pretty good job of determining who rides in a given vehicle, which is probably commercially-useful information.

The issue is the cellular modem built into most cars nowadays. It can vary in difficulty to disable or remove, with the added bonus of potentially taking other services that are attached to it such as Bluetooth. It fucking sucks. I don't know more details than that.