I’m not convinced that is completely accurate. The UC residency policy is here:
https://www.ucop.edu/uc-legal/_files/ed-affairs/uc-residence-policy.pdf#page=11
The most pertinent exception is for kids of a divorced CA resident parent who went to high school elsewhere:
“ 4. Non-Resident Dependent of a California Resident (Condit Bill) – A Student who has a Parent who both satisfies the Residency Requirements and either claims the Student as a tax dependent or continually contributed court-ordered child support for the Student during the one year immediately before the Residence Determination Date shall be eligible for a limited-duration Residence Classification for one academic year. A Parent who relocated to California must have severed any and all ties to their former residence; refer to “Sec. III. 1./2” The Student may thereafter be eligible for a Resident Classification if the Parent continues to satisfy the Residency Requirements and the Student has demonstrated timely fulfillment of the Residency Requirements. This provision requires that Students submit a new SLR at the end of their Condit academic year per campus policy. Students who fail to concurrently fulfill the requirements will be reclassified as Nonresident which is not eligible for appeal review. Students who have lived in California for more than one year after turning age 18 are not eligible for this provision.”
I think you need to examine this a lot more closely but it is at least possible they could get resident tuition at UCs after graduating from their current OOS high school if their CA resident parent is providing child support. There will need to be continued dependency on that parent during college, so if they don’t contribute anything to tuition that will be problematic. Call and ask about the “Condit Bill” exception.
There was a similar thread a long time ago: