Style guideline: https://musicbrainz.org/doc/Style/Release#Medium_title

Edit https://musicbrainz.org/edit/110684916 has shown that the current wording of the medium title guideline, "'CD n' or 'Disc n' should not be entered as a medium title," can be interpreted to mean, omit "CD n" from medium titles, even if the release itself has multiple media of the same title and even labels these as CD 1 through n.

Suggestion: reword the passage to read (improvements in italics),

"CD n" or "Disc n" should not be entered as the sole medium title without any other title text, and they should only be entered to distinguish between media of a release that share the same title.