What makes you say that, did you read the paper and find flaws in their methodology? Or does it disagree with your preconceived narrative and dismiss it out of hand?

I read the UC San Diego summary. As far as I can tell, their data is from an online poll. It’s well-known that online poll respondents are generally more interested in politics than average. It stands to reason that those considering leaving California may be much less interested in politics and thus undersampled. I didn’t see this potential sampling issue addressed in their write-up, though I’m a layman unfamiliar with the polling methodology they’ve used.