Yes but if someone went to those lengths they could just use a hidden camera. My fear is not some very unlikely determined person secretly recording my conversation, my fear is giving every single person in the world an easy tool that they will use that can also secretly record conversations.

Hidden cameras exist, but there is very little reason to use one in everyday. But giving every single person a thing they have constantly that does this functionality is a real change. The linked article mentions how cameras were banned, but I still dislike cameras and if I see people with one in public taking photos I will avoid them. If those cameras were always out and always pointing at people I would feel very uneasy.

As far as I know (which is very little), you're right - disabling the ability to produce light doesn't disable the camera as long as the software thinks the light is on. There are likely hardware-only approaches but they may be prohibitively expensive for a feature no customer wants to pay for.

That's the big difference between designing a light for the owner's protection (who probably won't disable the light and will notice if it breaks) versus a light for the protection of others (who might not know to look for a light in the first place, especially once Glass evolves to look like regular glasses).

There's a laptop accessory market for physically blocking camera switches with state determined at glance. Wearable cameras may need to adopt a similar mechanical approach for today's social expectations, but putting switches on your face is somewhat at odds with designing away from the Glasshole Borg look.