You remain a CA resident for tax purposes as long as your domicile is in California. Your domicile is your main, permanent home. A person can have only one domicile at time. You were clearly domiciled in CA prior to your move.
Your domicile does not change until you abandon your domicile in CA and establish a new domicile in another state. Your new domicile is established when you begin living in your new home in the new state. That is the date you become a resident of the new state, and cease being a resident of CA. It is not established by the date of your new drivers license, car registration, etc. That is because some people wait weeks or even months after a move to change their DL or license plates.
You didn't say when your move occurred. If it occurred in 2020, you will have to file a 2020 CA tax return as a part-year resident.
With regard to the "six month rule" you mentioned, CA Publication 1031 actually states, "You will be presumed to be a California resident for any taxable year in which you spend more than nine months in this state." https://www.ftb.ca.gov/forms/2019/2019-1031-publication.pdf , page 5
But that only applies to individuals who are domiciled in another state and living in California temporarily. It does not apply to your situation.
You'll find a good discussion of the concept of "domicile" in this reference: https://www.halversontax.com/residency-domicile-issues/#:~:text=California%20Code%20of%20Regulations...
Finally, CA will refund any excess withholdings when you file your 2020 return.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
