Yes, some security researchers at Johns Hopkins found an issue in older models (before 2013) that was since fixed and now it's should be impossible to circumvent it by software. https://daringfireball.net/2019/02/on_covering_webcams
As a former colleague pointed out: If some on is so far into my computer that they can disable the camera LED and turn on the camera, having leaked pictures of me walking around in my underwear is the least of my concerns.
He had a point. We're so afraid of bad guys spying on us using the built in camera that we forget if they are so far into our machines they can steal pretty much everything else.
I wish the camera's power circuitry were set up such that the LED were an integral part of it, so the LED failing would make the camera inoperable too.
The camera probably still gets voltage without the LED turning on, I remember a Louis Rossmann video where a Macbook failed to boot because of an overcurrent-caused defect in the camera.
The funniest thing about that was the fuse protecting the camera was intact.
There is a physical indicator LED for the camera. The LED indicator can't be seen if the camera isn't in use. Try launching Photo Booth and you'll see the LED indicator.
But, the latest Macs don't have a LED for the mic, which is a disappointment. Good old MacBooks had a LED indicator for the mic.
EDIT: sorry, my memory failed me. The old MacBooks didn't have a LED for the mic. On white plastic MacBooks (2006), there's two black dots around the camera. The dot on the right side is a LED for the camera. The dot on the left side is the mic, not the LED indicator for it. Thanks for correcting me!
This is not actually "hardware disconnected", more like "firmware disconnected". Consider Purism Librem 14 if you actually want a hardware kill switch.