I see it as fairly benign.

It requires the device/computer have a way to set the age. If you don't want to set your real age, that's fine. If you are a kid, your parent will probably have set it for you (it's really a feature for the parent, and they don't have to use it).

It then establishes that apps can know your age group, sufficient to comply with existing (and I suppose future) content age-restriction laws (where today they can dodge and say they did not know).

It's a pretty incremental step, and fairly minimal (in the range of all options proposed around the world). We can try it and see how it goes.