That approach has its own problems, mainly in increased complexity (i.e. more things to go wrong
The complexity & reliability of having two side sticks moving in tandem isn't a valid argument; yes there's more to go wrong but you'd hope that risk associated to this would be miniscule.
limited benefits, once the design is understood as a whole
From a training perspective, I'd say say there are huge benefits to having them both move, as cadets rarely understand the "design as a whole" from the outset!
It's still a very safe aircraft!