The bill authorize it using any technical means, specifically mentioning using classified methods («prescrire le recours au moyens de l'État soumis au secret de la défense nationale»)
Unless the light is physically connected to the power line of the camera sensor (and most aren't), it's useless as an indicator of covert camera usage - the spyware can just not turn it on.
Not on Android devices, but wasn't this what Apple said they did for Macbooks? That the light indicates power is going to the camera, and cannot be bypassed?
The privacy indicator on iPhones is just a green dot on the display. I don't think that's really possible to link to the same power supply. It'd have to be a separate light like on MacBooks.
(Thankfully MacBooks do at least physically disconnect the microphones if you close the lid.)
It could be independent of the OS software if it were a design goal (e.g. in safety-critical applications you sometimes have display controllers that have dedicated hardware layers for important indicators that are driven independently of the main display feed, something Apple could easily replicate given their level of integration)
And of course it doesn't have to be on the display, given they already have a cutout island in the display where they could place such a thing.
The green dot is meant as a privacy indicator - it tells you when something (camera, maybe mic?) is on. It doesn't relate to "remote" activation, and presumably would turn on in all circumstances.