IIRC from past reading, the driving factor behind the California bill was that some places were passing laws that would have placed responsibility for age verification on websites. Meta

probably correctly assessing that anything they did was going to be defeatable and not wanting to engage in a big fight with regulators over that

drove the California effort to create an OS-level responsibility. It's not that this especially solves anything from the standpoint of people who want age restrictions, but that it dumps the legal problems on the OS vendors, like Apple and Microsoft, instead of on Meta.