A couple questions- what portion of the workshop attendees self-selected from among people who were already interesting in rationality, compared to the portion that randomly stumbled upon it for some reason?

And even if it were from outsiders... I suppose that guards against the specific post-modernist failure mode. I think the checking by having to explain to outsiders isn't the most important thing that checks engineering, though: the most important one is having to engineer things that actually work. So rationality producing people who are better at accomplishing their goals would be the ideal measure.