"0 - Off (default). use standard native resolving"
...
"5 - Explicitly off. Also off, but selected off by choice and not default."
It seems that the plan for the "0 - default" is to switch the users to other modes without the user knowing it, and to keep the behavior off the user must specifically change the option to "5."
or...
It could be prepared for when the user gets asked what they want and then Firefox can remember an explicit "no" as compared to not selection ever made.
/ Daniel (author of the blog post)
Daniel’s own decisions aren’t in question here. If he works for Mozilla he is not more powerful than the whole company.
Having “off” and “off when selected by user” but not other variants still points to the intention of the default state not remaining off. Which is not problematic. Problematic is however naming the state that will obviously be changed “off.”
That's arguably rude, but then your follow-up is exactly the type of conspiratorial bullshit he's implicitly accusing you of, so it was just foresight after all I guess.