The COVID-19 workplace safety standards remain in effect in California until January. Under the updated temporary emergency standards, most employers do not have to require workers to wear masks if they have been fully vaccinated.  But there are potential legal and regulatory hurdles that come with trying to determine who has been vaccinated.  In order to avoid these concerns, it might be easier to just continue to treat everyone as non-vaccinated and continue to require the use of face coverings.  Essentially, just because OSHA said you can allow vaccinated employees to remove the mask, it isn't a requirement.  An employer can still determine what rules they will follow.