The symptoms of a full stall are fourfold viz nose pitch down, heavy buffet, high rate of descent, possible wing drop - one of the big clues other than attitude should have been high rate of descent - have never thought much of efis VSIs - the old display was far more noticeable.
Of course amount of buffet depends on type etc.
But the error chain started the moment the nose pitched up - basic flying says maintain the correct attitude.