They have never clarified what they're doing that is not
really selling data but legally "could be considered selling data". I understand that's how they tried to spin it, there's a very telling update[1] written two days later:
The reason we’ve stepped away from making blanket claims that “We never sell your data” is because, in some places, the LEGAL definition of “sale of data” is broad and evolving. As an example, the California Consumer Privacy Act (CCPA) defines “sale” as the “selling, renting, releasing, disclosing, disseminating, making available, transferring, or otherwise communicating orally, in writing, or by electronic or other means, a consumer’s personal information by [a] business to another business or a third party” in exchange for “monetary” or “other valuable consideration.”
That California definition is pretty much the most straightforward legal definition of "selling data" I can think of. That they describe it as "broad and evolving" makes me suspicious of their whole discourse, I don't think I can take their communication as 100% in good faith anymore.
Don't get me wrong, even after this I still use Firefox and I think it's better than Chrome in the privacy axis. But it's really annoying that they're still trying to paint themselves treating your privacy as sacred when that's obviously not the case.
[1] https://blog.mozilla.org/en/products/firefox/update-on-terms...