This isn't about what's in their best interest. Google has no way of knowing what analytics are being collected on websites they do not control.

Surprising, given they’re able to know more or less everything else about those sites. If their scraper can track Core Web Vitals why can’t it track Core Privacy Vitals? A cynic would suggest it’s because Google considers itself better off not knowing.

So your suggestion to fix concerns with privacy and tracking is that they should do more tracking?

I’m saying it’s the approach Google takes to every other problem and it feels notable that this is the exception.

Oh so google DOESN'T have a surveillance apparatus embedded in nearly every website that exists that by design sends them as much data as possible even on third party sites?

Or did you forget about Analytics.