I would expect that the default search engine deals that Firefox mostly relies on for financing could be interpreted as such.

Mozilla gets money, and as a result of the deal, the searches (data) of anyone who didn't change the default go to the company running the default search engine.

By default Google gets not only search but everything entered into the address bar (for "suggestions").

Yeah, that's pretty creepy - that also includes private that that would otherwise not reach the internet.

It is always the same idea - if the data is even slightly touched and/or processed, it is suddenly not a personal data anymore and is "ok" to be sold.

>What "sale of data" falls under a legal definition but would be understood by everyone to not be selling data? An example?

I assume probably data that's anonymized (in some sense) and/or aggregated (in some sense). But there's so much grey area there that it's a lot less reassuring than a straight up blanket statement that they used to be able to make.

The real problem is that they are collecting too much data in the first place. Really, the company making the browser should receive no data at all - even auto-update servers can be handled by other non-profit organizations like universities.