Here is a better way to word this from the publication for California:
https://www.ftb.ca.gov/forms/2019/2019-1031-publication.pdf
Nonresidents of California are taxed only on income from California sources.
Wages and salaries have a source where the services are performed. Neither the location of the employer, where the payment is issued, nor your location when you receive payment affect the source of this income.
A nonresident’s income from California sources includes income from a business, trade, or profession carried
on in California. If the nonresident’s business, trade, or profession is carried on both within and outside California, the income sourced to California may be based only on the business conducted within California, or may be determined by using the apportionment formula for corporations engaged in multistate businesses.
