Gnus: (documentation) bug? gnus-extra-headers

[D]

Hello all,

I'm a bit lost trying to comprehend the functionality gnus-extra-headers
supposedly provides.  No matter what I do, I cannot seem to get score
files to accept extra headers at all.  What's worse, gnus very clearly
does not seem to parse them at all.  Is there some configuration
missing?  To give a small working example, from emacs -Q:

the gnus init file simply reads

(setq gnus-startup-file (locate-user-emacs-file "gnus/newsrc")
      nntp-authinfo-file (locate-user-emacs-file "gnus/.authinfo")
      gnus-dribble-directory "~/.cache/emacs/gnus/"
      gnus-kill-files-directory "~/News/kill/"
      gnus-select-method '(nntp "news.eternal-september.org"
                                (nntp-open-connection-function
                                 nntp-open-tls-stream)
                                (nntp-port-number 563)
                                (nntp-address
"news.eternal-september.org")))

(setq gnus-extra-headers '(To Cc Keywords Newsgroups Organization))

Trying to use a line involving any one of these extra headers for, say,
Organization, does not work.  That is, a score file like
(("extra"
  ("." -5 nil r "Organization")))

won't score any article at all, independent of what I enter.  However,
the header is very clearly there in various posts (as can be checked by
the header itself).  What's worse, adding the format specifier "%~(form
(gnus-extra-header 'Organization))@" (as mentioned in the manual) to
gnus-group-summary-line-format reveals that the extra header is never
recognized at all, always returning the empty string.  Yet, variables
like gnus-visible-headers (which take strings instead of symbols,
granted) accept Organization no problem, and display the correct value
in the articles that have the header.  Is there some missing flag that
I'm missing?  I very much doubt it's a bug...

Cheers,
D.