The real reason it doesn't qualify, though, is that my HOA—my entire city of ~650 SFH homes exists behind an HOA—has stated it won't approve SB9-related lot splits. The city itself wrote SB9 language into its bylaws, as required, but the architectural review committee in the HOA won't approve requests.
Moreover, all homes in my city are on septic systems, and LA County has a min lot size requirement for approving new ones. Some lots are large enough to split without dipping under that threshold, but most aren't; that means we have a sanitation reason to reject lot split requests too.
I imagine that similar developments will block lot splits in these ways. Have you run into similar issues? Have you successfully split any lots yet?