From TFA:

> Someone once said that SF is a town of extremely high sincerity, and all of its modern and historical weirdness — the AI doomerism, the cults, the hippies, the drug use, the polycules — is downstream of people saying things and other people taking them extremely seriously.

This is a perfectly reasonable usage - perhaps not the Hallmark greeting card one but it's certainly valid.

> the difference between the east coast and the west coast.

Having lived in and visited places on both sides of the US I can safely say that there is no single "difference" between them and that treating both as culturally monolithic (or their constituent places as broadly similar) is a massive category error. Boston is not Miami is not Atlanta just as San Francisco is not San Diego no matter how many people confuse them because they both start with "San".