This has been proven incorrect, time after time.
That (old!) article is about modifying a 2008 (pre-unibody) model Macbook Pro. That (with earlier models) had a camera that was enabled totally by software, and the LED was (in theory) possible to re-program on those models.
Since that time (nearly 10 years ago) the unibody and retina model cameras have a power LED. The LED on the newer design cameras indicate power, and illuminate when the camera has power. If the LED is not visible, the camera does not have power. It's not possible to bypass that through software methods.
You COULD, if you have local access to a MBPro, open the case, and modify the camera physically by disconnecting the LED. Pretty sure the connection is on a the tiny circuit board with the camera, so you would need some good magnification to find the correct link. As the display assembly is mostly glued together, that would take some time (and repair parts when you break something
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). And, highly unlikely that you could hide the job from the user.
Of course, bypassing the power LED is a moot issue if one is just taking pictures, the camera only needs power for a second. So, the camera could be turned on, take the picture, and turned off. The user may not ever notice the camera LED was even on, for that second or two.
This is where the bit of tape over the camera will ALWAYS prevent pictures/video.