There's no standard that I know, that, like "Secure EFI / Boot" (or whatever exact name it is), locks the API of periphery firmware and that would be able to statically verify that said API doesn't allow for unintended exploits.
That being said: imagination vs reality: the Turing tarpit has to be higher in the chain than the webcam firmware when flashing new firmware via internal USB was the exploit method.
(Source: I architected the feature)
> Macbooks manufactured since 2014 turn on the LED whenever any power is supplied to the camera sensor, and force the LED to remain on for at least 3 seconds.
That convinced me originally I think, good old days! I'd almost forgotten about it. The way you phrased it, it sounded like 50% OS concern to me.
But if cam & LED rly share a power supply, and the LED is always on without any external switch, Good then!