It's both. Seattle is one of the most introverted cities in the US (socially, it's disproportionately shaped by the tech population). Seattle Freeze is a real thing. COVID also did a number on people worldwide.

Also, gloomy weather 7-8 months of the year makes you not want to socialize.

I don't know if tech has anything to do with it. The Yemeni coffee shops in the article have been thriving for years in San Francisco

Supposedly it's Seattle's scandinavian origins. Obviously Seattle is a big coffee town but the cafe vibes are definitely different from SF's, or LA's.