There really isn’t a ‘ban’. CA private schools that still consider legacy can’t get state financial aid assistance for their (CA) students…so these schools have to fund the difference thru their institutional aid. Stanford has also said admissions will continue to consider legacy, at least for this cycle. All the CA private schools have to report compliance and legacy data to CA each year as well.
Anyway, I agree with you that this is $$$ driven. I assume that these schools receive greater $ from legacy families than they receive state financial assistance for CA students (OOS/int’l students wouldn’t qualify for CA state aid.)