Switching it from passive to active means you can count it towards https://github.com/bslassey/privacy-budget . Yes, sites can ask for all sorts of things, but if they ask for enough that they could plausibly be fingerprinting you then they start seeing their requests denied.
(Disclosure: I work at Google, speaking only for myself)
So why not still send limitied information by default in the User-Agent header, and if they ask for it, send more information in User-Agent header? (keep everything in one spot?)
(Disclosure: I work at Google, speaking only for myself)