The only way to prevent this in any way would be a light sensor on the other side of the case which you could use to check the Indicator when the laptop is closed. But if you can’t trust your hardware to that level, there are thousands of other attacks you can do.
On the iPhone if you observe closely, it is drawing a green circle on the screen area where you normally see portions of your OS or app. It starts with a tiny circle and grows until it becomes a certain size. When you close the camera app, the circle turns orange and shrinks until it disappears.
On the Macbook, it is a bright green circle that just turns on like an LED and is located in the cut off portion of the screen that has nothing software related in it. When the camera using app is close the circle just disappears like an LED turning off.
It is not. What gave you that idea?