This reminds me of some dev tools (can't remember which ones) which require the user to do something like set an environment variable to "YES_THIS_IS_A_TERRIBLE_IDEA". If the switch to disable aircraft automation involves such cognitive barriers, it's possible that pilots could be relied upon not to use it except when truly necessary. Heck, the barrier could be that pilots aren't told of its existence until contacting maintenance. It sounds silly and useless but it would have offered greater assurance in this situation that landing could be done safely.