(However, it's certainly possible to imagine someone who can signal "being a physicist" without having learned interesting things about physics (fake PhD) or vice versa (extremely skilled autodidact), which why I think they're probably two separate but related functions.)

I think the Physicist Conspiracy in which I am a member with my PhD and all does NOT require a PhD to join. Freeman Dyson for example is clearly accepted in the club despite never bothering to get a degree beyond B.A.

I hope that the cynicism I reject in my own self-examination of my membership in my own church of rational physics engineering leads me to reject cynicism when trying to understand other people's churches. There ARE reasons people believe things and they are by no means all stupid reasons.