I wasn't aware of that, but perhaps it will hearten you to know that I don't deal with warranty law in my day-to-day. So, I clearly have more to learn - not sure why you felt it necessary to call my credentials into question over it though.
But in any case, your post does strengthens my main point, which is that fear over surveillance of vehicles by OEMs, with no consumer recourse, is somewhat overblown.
EDIT:
Just read Magnusson-Moss, and I have a question since you seem to know about it - you said the act "makes it blatantly illegal to 'void' a warranty for any modification, unless it can be proven that the modification caused the issue that the customer is making a warranty claim for."
But the act itself says "the warrantor shall not impose any duty other than notification upon any consumer as a condition of securing remedy [...] unless the warrantor has demonstrated [...] that such a duty is reasonable." 15 U.S.C. § 2304(b)(1).
Based on what's actually in the text of the law, I could imagine Tesla or some other OE making the argument that it is "reasonable" to condition the warranty on the consumer continuing to feed the stream of telematics data to the OE, because it allows them to identify warranty issues before they require substantial repairs, thus potentially saving significant money for the OE, and significant time for the consumer - certainly a reasonable thing. I personally don't agree with that argument, but I'm curious how you would respond to it, and how you can be sure that a court would shoot it down.