If you look through the old mailing list postings, the oft-left-implicit problem with Klingon (as well as Tengwar, Everson’s [EDIT: misspelling] pet project) is

If you look through the old mailing list postings, the oft-left-implicit problem with Klingon (as well as Tengwar, Everson’s [EDIT: misspelling] pet project) is that it may get people into legal trouble (even though in a reasonable world it shouldn’t be able to). So in the unofficial CSUR / UCSUR they remain. A weird solitary character from the 1400s isn’t subject to that, and even if it’s a mistake it’s probably not worth breaking compatibility at this point (I think the last such break with code points genuinely changing meanings was to repair a mistaken CJK unification some time in the 00s, and the Consortium may even have tied its own hands in that regard with the ever-more-strict stability policies). Similarly, for example, old ISO keyboard symbols (the ⌫ for erase backwards, but also a ton of virtually unused ones) were thrown in indiscriminately at the beginning of the project when attempting to cover every existing encoding, but when the ISO decided to extend the repertoire they were told to kindly provide examples of running-text (not iconic) usage in a non-member-body-controlled publication. (Crickets. The ISO keyboard input model itself only vaguely corresponds to how input methods for QWERTY-adjacent keyboards work in existing systems—as an attempt at rationalization, it seems to mostly be a failed one.)