True. It's harder to fake rationality than it is to fake the things that matter today, however (say, piety). And given that the sanity waterline has increased enough that "rational" is one of the most desirable traits for somebody to have, fake signaling should be much harder to execute. (Somebody who views rationality as such a positive trait is likely to be trying to hone their own rationality skills, after all, and should be harder to fool than the same person without any such respect for rationality or desire to improve their own.)