Your chapter 3 Aircraft Antenna Installation reference is NOT a Boing document, so it doesn’t apply to the 777. Oxygen tanks are turned off and on only for servicing and there is a cockpit indication of oxygen pressure that the pilots verify before departure according to their checklist. These crew oxygen tanks are not accessible from the cockpit.
Look, I am not trying to be disagreeable and I trust you to work on mu avionics anytime, What you post is entirely correct but not germaine. I am talking about errors made by people using technology, not the technology. All I am saying is that this scenario I laid out is the simplest explanation and entirely consistent with human behaviour.