Since you never worked in California, none of the income would be taxable there. It would be different if you worked there and then moved away, then your stock option income would be forever taxable.
It comes down to "California Sourced Income", which means income earned when you worked in California.
You can read more about it here, see E. Stock Options:
https://www.ftb.ca.gov/forms/misc/1100.html
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