If you turn a single family home into 10 condos, you'll probably get a bigger combined assessment, and also more frequent turnover. Prop 13 actually would encourage this.
If your turn it into apartments though, you've probably eliminated turnover, since it's much easier to own apartments through corporate forms that won't trigger a reassessment.
The result of your policy is not only increased cost of housing and underdevelopment, but higher sales taxes as well. If California had a more healthy proportion of property taxes, then sales taxes wouldn't be forced up to nearly 10% to fund government.