if I have headphones or speakers or a mouse that aren’t plug and play on Linux which is what I’m used to on windows, I think it’s fair to say that my experience with Linux is less easy than with windows.

If that were the case, i would agree, but I dispute this claim.
Can you tell me specific models of headphones, speakers or mice that are not plug and play in any modern widely used distro?

That’s obviously not what enabled means, at all.

If there is a button visible that executes a function when receiving a click, that feature is enabled.
That does not mean that the feature is actively in use, of course. Enabled and active are different states for a program’s functionality to be.

I believe it’s pretty easy to understand, there are people like me who don’t want to have AI functions popping up in our browsers without explicit enabling on our part.
I understand that you disagree, but it is not a difficult position to understand.

You don’t need to re-define opt-in and opt-out just because you support Mozilla in adding AI features to Firefox.

In my opinion there is no ambiguity at all.
Opt-in means that the feature is disabled by default and until the user enables it. This is NOT what Firefox will be doing.
Opt-out means that the feature is enabled by default and can be disabled by the user. This is what Firefox will be doing.
Whether the user actually uses or not the feature is not a factor in determining if it is opt-in or opt-out.