There's no substitute for a hardwired camera-on indicator light.
Otherwise politicians are going to keep showering on camera during meetings, instead of showering off-camera during meetings, like they're supposed to.
I know that the webcam USB API requires the on-off light to be controlled in software, but can't webcams just... Ignore that, and just control it in hardware? It seems to me that would be better for everyone. Heck, we could mandate webcams have hardware indicator lights by law. You can always tape over them if they bother you.
It's kinda a mix of things. Webcams built with IR sensors and emitters (like the Logitech BRIO 4K) don't use the indicator while using the IR, though you can clearly see the pulsating near-infrared LED while it's on.
On Linux at least, if you open the v4l2 device for a device like this, it will turn on the indicator directly, and I don't think you can attach to it with libusb while it's otherwise in use by v4l2. In practice, I think the worst you could do from userspace on Linux is show the indicator while not recording.