My situation was right out of the CARB and DMV procedures and rules. It is to keep non-CA emmissions compliant cars out of CA. Has been going on for years.
One thing I found out was that if I tried to register a motorcycle with some kind of problem (non-compliance or ?, can’t remember), that VIN would be flagged, and that motorcycle could Never be registered in CA.
I know they are currently getting away with forbidding older diesel trucks from even entering CA.
I really do not think they have that power under the interstate commerce clause, but it seems no one is calling them out on it.
I escaped Kali-fornicate-ya in 1989.
NOTHING would entice me to return.
Sadly, every sane person who flees makes it that much harder on those who remain.