Huh.
Ok... I think I have an explanation for 'ya know'.
Its a zoomer/alpha thing, not a millenial thing.
PNW is kind of notoriously 'way too online' and we suck at / hate talking to people we don't know already, in person.
I think the 'ya know' thing that you are talking about, I think that was basically a tiktok thing for a while, basically a meme.
So... that's my guess there: its essentially a meme that worked its way into the vernacular of the 'way too online' zoomers/alphas of the PNW.
'Pre-funk'... yeah I remember that starting to catch on, and being annoyed by it, lol, because it literally just is 'pre-game'... I don't use that phrase, but yeah, a lot PNW people do.
Also, its funny: I'm in the Midwest now... and because I am actually capable of striking up a conversation with people I don't already know, in person, yeah, people do seem to guess that I'm from Cali, more than they guess Seattle.
So if you're saying people assume 'talkative = Californian"... I guess that would mean that I actually have something resembling 'normal' social skills, at least in comparison to the PNW hikkikomori, hahaha!
I was talking with some older dude recently, with an accent ... I think he said Kentucky... but goddamn it, after we got to be a bit friendly, he started rambling off ... I literally could not understand a word he was saying, for like 30 seconds of him talking.
Accent was waaaay too thick for me to decipher.