Bonin in his panic hit his priority button to take back control but didn't say he was taking back control. He should have announced he has the controls - and it is obvious knowledge to pilots that flight behavior us from the averaged stick inputs. But only when they know both are handling flight surfaces.

If a pilot stubbornly wants to keep control maybe out of desperation or panic - and performs actions which are counterfactual to the knowledge of aerodynamics every pilot is taught, there is no instrument system which can salvage this catastrophe.

["Bonin acted like an idiot" - not my words, but two of my CFI friends, who discuss aviation topics on weekends often over beers.]