This seems like a cultural mismatch more than anything. Mozilla makes software that human people use and human people use normal language rather than avoiding the non-profitable aggravation associated with emotive language that a company employee might be used to.
Look at the point that op made instead of the tone: the AI feature should be opt-in not opt-out.
That's a good point. Let's talk about that. It seems like it's a simple thing to do to show good faith that this won't be a normal corporate AI push.
It's not a good point. One year from now, every browser is going to be an "AI browser". If Firefox will make it harder to use features that are expected of every browser, it will lose. This is akin to saying that JavaScript should be opt-in. If you want to disable these things, you're clearly a power user, and you should at least be comfortable with clicking "Edit" and then "Settings".