I disagree with the 90% number for the LVT switch on multiple fronts: for starters all the people with historical discounts will pay more. Secondly, the typical SFH pays more and there is a lot of SFH in California.
LVT is still worth doing but making it actually happen is politically difficult in the best of states and California is the worst one due to Prop 13.
You seem to be ignoring that the presence of the corporate HQ raises land values across the entire city. Landlords of high density apartment complexes should be applauded for not wasting precious land in locations where many people want to live in, using land wastefully increases rental payments and causes homelessness.
But...California has a tiny overall property tax rate. A revenue neutral change to an LVT (unless it's revenue neutral on the far side of the Laffer Curve) might better meet some abstract concept of fairness better, but isn't going to have a meaningul impact on price of... anything.
There are ways to fix that too with gradual phase-ins, not allowing people to pass their tax assessment on to their heirs, etc. But anyone who stands to inherit property will vote against such a move, and most people who will be passing along that property will vote the same way.
Why is regressive property tax better than the progressive income tax?
If you also tax the improvements to the land, you discourage people from building denser housing on it, because the tax itself goes up the more you build.
I think it's close to “for 90% of people who pay property tax that would be a tax increase”; the people it will be a tax cut for are the people with relatively high improvement value on their land compared to the bare land value, like corporate HQs and landlords of high density apartment complexes.