Clarity is needed here. The California language that sparked all this is qualified with "about FakeSpot's products and services". Meaning it could simply be third-party services that they send their own emails through.
After reading their privacy policy, nothing jumps out at me that contradicts this.
To be clear, I'm not a fan of the extension's collection practices, but the down votes could be because this may be unwarranted fear.
Sure, but this doesn't mean much. If they didn't transfer ownership, FakeSpot could do whatever they wanted with that data. By forcing the transfer, Mozilla can choose to keep it private.
Use LibreWolf, it's Firefox without all the garbage like telemetry, Pocket or Sponsored Sites. It makes substantial privacy and security improvements and comes with uBlock Origin pre-installed.