I'm going to dip my toe in the water with a (former) cabin crew perspective. Don't be too harsh!
Firstly I understood and respected the chain of command. I also understood the importance of keeping the flight crew in the communication loop; that their situational awareness could only be enhanced by a clear description of whatever might be happening in the furthermost reaches of the cabin.
The training I received encouraged cabin crew to work on their own initiative when the situation demanded it. If the situation was clearly catastrophic,(and this was very well defined) then you commenced an evacuation even without the Captain's command.
However training also underscored other greyer areas. That you may be involved in what seemed like a 'contained' emergency that suddenly and without apparent warning deteriorated into something immediately life threatening. Where reaching for the interphone might mean you get to find out exactly how fire retardant your polyster mix uniform actually was. Obviously initiating an evacuation when the aircraft was moving, had the engines running or indeed had several thousand feet of cloud beneath it was best avoided. I think the best advice I was given was - if you are thinking 'should I?' then don't.
In my experience training was very concentrated on in flight emergencies and less on ground based ones. 180 passengers 25,000ft up have little option but to listen and be directed by crew. Good communication under these circumstances is relatively easy. However transfer the situation to the ground where the passengers know they are on terra firma, sense impending disaster and want a swift and immediate exit and you have a very challenging and dynamic situation in the cabin. Under these circumstances communication is far more likely to break down and hasty, incorrect decisions made by the cabin crew. I don't know what the current sep is like, I'm a couple of years out of date, but I think it's a training area that needs to be explored thoroughly.