This statement has a number of issues. First, you have to trust Apple that the indicator _really_ can't be disabled. You also have to trust that there isn't a vulnerability Apple is not aware about that could allow rolling the camera without the light coming on. This has happened in the past [0] and there are known Apple products that are vulnerable, yet the statement never mentions this making you believe it's impos…
I'm not disagreeing with your other points nor am I saying that this isn't the case nor am I a fan of any apple products... However designed circuits to implement such functionality is quite common.
[0]; https://en.m.wikipedia.org/wiki/Series_and_parallel_circuits