Non-essential communications are rarely good in incidents like this. The people who know things and can do things are to busy finding those things out and acting on them to keep everyone in the loop. So if you get the information that you need to survive, the rest is gravy.
While untrained passengers can behave unexpectedly, their behavior mostly falls into a predictable range. If the cabin crew is faced with a situation where passengers start self-evacuating, they either have a nutcase on board, or they have demonstrably lost control of the cabin.