the key then is to attempt to prevent that fully separated wing stall from occurring
The problem is that there is a basic and unavoidable trade-off between prevention and cure. The human body is designed to avoid falling, but once you go off that cliff human's don't sprout wings. Likewise, a bird is designed quite well to deal with falling but doesn't have many features to prevent it from falling in the first place.
The problem then is that as you increase the complexity of the systems to prevent that wing from stalling you also increase the risk that when that prevention fails (and it will inevitably fail sooner or later) there is no cure left.
Mother nature cannot be fooled and one thing it's foolish to believe is that you can design a perfect system. It's always a question of trade-offs, of robbing Peter to pay Paul.