I only questioned your credentials because you said you were in legal counsel,
and at an automotive OEM of some kind. Most people who've done any significant DIY car work know about this law, because it's protected them for decades from dealers that would try to deny them warranty coverage for completely unrelated non-dealer repairs or maintenance. For instance, a dealer can't claim that some kind of engine trouble isn't covered because you replaced your own brake pads, or worse, because you replaced the radio. They also can't deny warranty coverage just because you had an independent mechanic work on your car instead of the dealership. Furthermore, they can't require OEM parts to be used, unless they provide them for free. I would have thought anyone working in automotive legal would know about this off the top of their head.
As for your example, that sounds pretty contrived and ridiculous to me. Doesn't mean someone might not try it though; companies have tried lots of ridiculous legal tactics before, such as Oracle's current API lawsuit. But I imagine any decent court would shoot it down pretty quickly. Warranty claims are made because parts fail before the warranty expires; the absence of telematics isn't going to magically make some mechanical part fail faster. It might help identify it sooner, sure, but it's still a defective part for failing that quickly, so I don't see how the consumer disabling telematics absolves the manufacturer from covering this. In short, it's never been "reasonable" before this for car companies to have telematics to keep their machines working properly through the warranty period, so why is it suddenly required now? It's not reasonable for anything else either; does a new house need telematics for the house warranty to be valid? How about a blender or toaster in the kitchen? I don't see this argument going far at all.