Who orders the exits opened?
I am in a SWA exit row seat about 2 times per week. I get the briefing which always includes " no crew member will be here to assist you" . No where do they say "wait till the crew orders the emergency exits opened" or anything to that effect. The passengers are referred to the emergency card which says check for fire or smoke before opening the exit.
So the passenger adjacent to the over wing exit is not expecting a command, simply to check for the presence of fire and smoke. So maybe it is not surprising the exit was opened before the engine was shut down.
Next flight I will listen to see if they say when to open the exit.