This subject has been raised many times. As a member of the Flight Safety Committee of two airlines, I raised the purely hypothetical scenario of an aircraft stopping in a hurry after some sort of failure or emergency and the cabin crew, upon seeing the smoke or flames outside the aircraft, then initiating an evacuation. If they manage to contact the Pilots, all well and good, but if not, consider what would happen if the captain then decided to taxi the aircraft clear of the position it had come to rest? Increase in power to move might very well ingest a fwd chute and the fan thrust would almost certainly rip any rear chutes from the aircraft.
Raising this scenario at several meetings was met with, 'This is the industry standard and considered best practice when it comes to initiating an evacuation, go back in your corner and be quiet'.
One day, many casualties will result from just such an event and the Industry best practice will be altered.
I have absolute faith that the CC who initiated the evacuation was doing the right thing, under present regulation.