I feel that neatly meets the kind of thing these params are for - if you ask a server for content and say "Accept: */*" the server should be free to return that content in whatever format it likes.
plus regardless of the official meaning, how _else_ would you interpret a header that's saying "I'll accept anything". Like the only reasonable response is "cool, here's what i felt like giving you since you gave me no guidance whatsoever and said you could handle anything"