1. X sniffs my connection.
2. X learns my address uses Firefox on Linux.
3. X sells the data to Y, whom I never visit.
4. Y correlates the IP with Z's subscriber data, and adds Linux to my shadow profile.
As the sibling said, the burden of proof is on them. They are the ones who push that on users when there's no technical need.
If you decide to visit google, that's your problem. Visiting mozilla should be optional too. Otherwise it creates attack surface area that wasn't there before.
Okay, so in conclusion, the attack vector from analytics that people spill dozens of comments on in every Mozilla thread is not unique to Firefox but rather shared with every website on the planet.
As the sibling said, the burden of proof is on them. They are the ones who push that on users when there's no technical need.