Not only is the latest point dated “October” but it describes average prices of all houses closed escrow during the three-month period ending in October. So, it’s a good indicator of the state of housing in September (or maybe even August, because September closings begin as August accepted offers).
It’s probably done that way because they have a wide coverage area (20 metro areas, I think?) and some places may be less computerized than others. Case-Shiller technology does not allow retroactive revisions of any officially released data points, so they have to wait till they get full sales records from every city before they release anything.
San Diego prices fell additional 5-7% across the board since September. But this is traditionally a slow season and interest rates are really low. I would not rule out some sort of stabilization next spring. It depends on how the economy is doing.