The economic term is "deadweight loss" and the most ideal scenario (outside of not having it) is to have both the supply and demand side share the deadweight loss equally. However, if either curve is out of sync with the other, then the portion of the deadweight loss paid shifts. So if a landlord can pass on 100% of the property tax, then demand is dramatically and catastrophically way outpacing supply. This is a bad situation to have if you want an efficient market where buyers have lots of choices and options.
Edit: I see where you might be confused - I'm talking about passing on 100% of the property tax. In an ideal scenario, landlords would have to cut into their profits to pay for the property tax that tenants wouldn't. But in California, we obviously don't want a market where buyers have lots of options, so apparently everyone is ok with landlords passing along 100% of the property tax cost to the tenants.