The application of age indication is just going to be another metric that these companies use for fingerprinting and person identification, one that some analyst on their inside possibly considered a useful data point.

And while this particular API might be an easy one to target, for removal as a patch, it might end up being part of a JS framework that many websites use and will break in case the return value is not available.

So if people require sites to work, this will become just another feature, requiring similar mitigations to other JS features I mentioned, that will need to be handled in a way that it increases the anonymity of the user, lest the user be subjected to harassment.

By "harassment", I mean the actual inescapable kind, not just random internet trolls.