FWIW while I'm playing hardball here I really appreciate your answer and expertise.
There is always a likelihood that data gets used for reasons beyond the original purpose. In the best of world the hardware that runs on consumers devices would do the right thing which would allow the web to be a perfect sandbox. I think we're slowly getting there, in terms of video it's slowly getting to a point where H.264 support is "universally true" rather than a minefield although VP9 and AV1 is a bit of being back to square one.
I think the spirit of my original comment was not to say "I promise that X company isn't doing Y" more to explain why this code existed in the first place. A search engine doesn't need to know what WebGL capabilities a device has as it doesn't deal with rendering whereas a site that has to work with hardware decoders most likely does need to know.
You’re actually just outright accusing them of lying.
Edit: this is the typical example of a loaded question, not an actual accusation against the parent comment https://en.m.wikipedia.org/wiki/Loaded_question
So when did you stop beating your wife?
You need to be able to tell the good from the bad and IMO you're wearing these trousers the wrong way round.
It's good to ask the hard questions and even though I'm not able to answer it in detail I still think that 'tmpz22' brought up a good point in that data can be used for both good and bad at the same time.