It explicitly doesn't, though they don't explain why not. It's not an on/off device distinction because it disables Firefox's automatic tab groups too.
A lot of anti-AI backlash seems to exempt machine translation, which as far as I can tell is just because it's been around for so long that people are comfortable with it and don't see it as new or AI-y, which imho spells doom for a lot of this- in ten years automatic tab groups will seem just as natural and non-intrusive as machine translation.
The local translation in Firefox is an NMT model, not an LLM: https://github.com/mozilla/firefox-translations-models?tab=r...
It's much more efficient on system resources than the larger LLMs downloaded by browsers for other tasks.
It's not mere familiarity. Machine translation is immediately useful to me. I was going to pull up google translate anyway; keeping it local to my device improves both convenience and privacy.
A local LLM that I explicitly bring up to ask a question and dismiss (ie no CPU or RAM usage) when I'm done consulting it is nice. A piece of software I'm using interrupting what I'm doing to ask me a useless and annoying question or to make an unsolicited change to my workspace leaves me thinking about permanently uninstalling it.
I will never want automatic tab groups or automatic anything else. I don't even want an "integrated" desktop environment - I use i3 to get away from that. I hate all the useless bullshit half baked features that are constantly shoved in my face.
If the modern web was compatible with it I'd use a text based browser for 90% of what I do online. And if that were the case I'd still welcome a built in machine translation feature because it's an incredibly useful tool.