> If we want to increase the percentage of effective non-impostors, we need the experts to learn to accept their expert status.

I'd argue that a good part of what helps some of these people achieve the expert status is their impostor syndrome. It pushes them to continue to be better all the time and never be satisfied with themselves (to a fault). Challenging them to "accept their status" is like telling them to change a core part of who they are.