A zero/zero ejection puts great demands on the 5' drogue to withdraw the main chute from the headbox. There is no momentum (speed) to provide the drag required to work at maximum efficiency. However- they do work and have done many times in zero/zero conditions. But if the scissor shackle was vastly over tightened then that is just one more difficulty for the designed sequence of events to overcome. Without the drogues being released there would be no complete man / seat separation as the main parachute cannot deploy despite the harness being released from the seat anchor points by the barometric time release unit operating.
I find it inconceivable that a pilot of his experience had wrongly routed the harness through the ejection handle.
I'm also not able to see on the Mk10b how the safety pin can be inserted and not lock the handle in its proper place- just doesn't work- if the handle is not in housing properly the pin doesn't fit.