Well, Mozilla recive money from Google, not only to use it as default search engine, it’s way deeper, so Mozilla send data to Alphabet, googleanalytics and googletagmanager, as said, if you create an account in Mozilla, Google also receive this data.
The Firefox save browsing API is also from Google, the same which also in the Cromiums, which in Vivaldi can be desactivated in the settings, like other Google APIs left to the user choice. Extern sponsores never are a good idea, it gives other the power to make decisions for the own brand. I hope that Mozilla manages to finish this contract next year, as intended.
Yes, Google can limit the lists which use adblocker extensions, eg uBO, but not the lists itself used by others. Anyone can use the filterlist he want. I think that also FF will be forced in the future to use an inbuild adblocker.