"Lane Filtering" was never addressed in Cali, it was something we all just 'did'. Much like Europe and India, It's a matter of practicality.
Recently the CHP "recognized" it as legal in Cali (CVC21658) in order for them to write "guidelines". Sorry for all the quotes, but their words matter. It's reported as a "law" but it isn't one.
Laws are written tho dis-allow stuff. Laws aren't written to allow stuff. Thank God. But I digress.
I'm pretty sure Utah passed a bill to allow lane filtering this year and a couple east coast states are very close. (Conneticut IIRC?) Things are thankfully changing. I remember Oregon has been close to passing it a couple times when I was up there. You'd think Washington with it's terrible traffic would benefit greatly, but who knows? It usually gets determined by a couple old senators who have never ridden anyway and perceive it to be scary for them in their cages. IMO, I think it's because they are startled by a bike next to them that they never saw coming... because cagers never check their mirrors
IMO, I generally follow the CHP guidelines just as a matter of self-preservation. It's not worth the risk to be going 80 between cars if they are all traveling 70 on the freeway. BUT through Santa Monica, I will go to the front of the line at every light and dramatically shorten my commute by just moving through the stopped cars.
Opto: Your throttle hand is your responsibility haha, and your CHP guy was right, sort of. Their "Guidelines" say use the left lanes, under 30MPH, and >10MPH speed differential... but you can't get a ticket because it's not any "law" you'd be breaking. That said, they have an arsenal of ways to stop someone from riding like an A-hole. Generalities like "aggressive driving" and "loss of traction" for wheelies and fast acceleration. I have a collection of those, wanna see?? LOL