It seems unlikely to me that Hollywood has an age discrimination issue. It seems much more likely that Hollywood has a looks discrimination policy, and merely hiding the numeric age of an actor or actress isn't going to resolve this.
If an actor doesn't look the age for a part, they're not going to get the role. Trying to hide their "real" age won't help with that. Nothing short of completely changing Hollywood culture - and, really, American culture - to not be so youth-focused will change that. And that's not an easy task, and certainly not something this law will help with.
This is clearly a "this is something, so we're doing something about the problem!" law. It won't help in any way, but at least it's a bullet point on some lawmaker's resume!