the proposed implementation leaves me questioning how useful the CH headers are for initial impressions of a web property if only the browser and version are sent by default, and more info is only provided on follow-up requests, assuming the user agrees to some permission popup they don't understand. it'll be the "this site uses cookies" nonsense / nuisance all over again. it'll finally push end users to install the native reddit app without those constant annoyances.
i have quite a few ux enhancements that need to know or guestimate the screen size, if the device is touch capable and OS (especially for form input styling). i dont see how it is possible without an additional delay, fetch request and some annoying permission popup to deliver a good experience in the brave new CH world.