According to the article, in a city of almost 900k people, only 5600 properties were sold?! I don't know what a normal number would be, but this seems incredibly low.
various incentives, e.g. waiting for more liquid cash to come in, also your property tax is tied to home value when you purchase the home, so if you bought a home in the 80's/90's and still own it, you're paying pennies in tax, which is a much better deal than you can get elsewhere, which disincentivizes people from selling
Subjectively, this seems like a big deal. I was fortunate to buy a small condo before the last round of rocketing housing costs. My low property tax bill definitely influences the calculus whether to sell. If the intent for current CA property tax rules were to reduce inequality, I think they have the opposite effect.
If you owned a house in SF free and clear and capped property taxes would you sell?