IF it were so darn dangerous to let people run around on the tarmac, then there wouldn't be slides to allow these people off the plane.
In the good old days with the DC9 and 727 one would use the onboard stairs. Now, there is no choice but the slides.
All airline pilots are now trained to avoid an UNCOMMANDED evacuation as there could be a problem with someone walking into an engine and coming out as hamburger.
The ground staff should have been read for an evacuation...and oh...if it had been vital to maintain radio silence, the ground staff could have plugged into the interphone system used to control pushback. OR as a last resort, had the pilot open the DV window and shouted to him.
Now, I don't even know what kind of plane is involved as my computer is old and I am going only on the transcript. But come on.
Some of you may remember a term used in security training...I won't even repeat it now. But the BOSS of security on the plane is the pilot in command. There is a ground boss too, but he has to work with the pilot...he might offer ideas but its up to the man on the scene...in the cockpit, what to do.