Yeah, at a couple of companies I worked as a middle manager we had training on how to manage people and they made a point of telling us to avoid the shit sandwich. That it's really not effective and managers use it because they don't feel strong enough to give the feedback without sugar coating it. My anecdata doesn't include enough points for me to be sure if it is effective or not, but those trainers who had seen large numbers of cases insisted it was ineffective.