Yes Fly26 - I totally agree. In fact it was my next step in teasing this out.
Only the Flight Crew (or anyone else on the FD at that time) could have known that NOW was the moment to act.
The apparent lack of stress in the crews voice(s) - if we are to believe the statements from the authorities who have reviewed the tapes - would seem to indicate there was nothing 'untoward' going on right up to the point of handover.
Or else the crew member making the transmission was remarkably composed under duress?