Ultimately it was determined that it simply was not practical to make an in-flight deployment controllable with the (then new) very high bypass turbofan engines, the only answer was to make sure it never happened. Hence the retrofit of the 'third lock' (aka 'sync lock', although not all installations use an actual lock on the sync cable).
Thanks again, very interesting.
You’ve reminded me, this was another point made by Green, trying to make sure it never happened.