I seem to recall some Mozillian saying this wasn't intentional and explaining why, but I don't have the link.

Funny how decisions which financially benefit the developer have a way of "accidentally" being activated by default. The automatic downloading of the Windows 10 update. Or these bundled Telefonica extensions in Firefox.

It's just a button resetting to the default position. That's easy to trigger as a side effect of any number of changes.

It's strange that other defaults weren't reset though.

My entire browser bar was reset. (I wasn't thrilled, but whatever, it's free.)

Firefox is developed in the open. It's easy to check if there was a deliberate change.

Of course there was a change, but that does nothing to tell us if the way it was activated was accidental or intentional.

Well, the commit message would be a clue. If we assume they aren't being deceptive.