The purpose for these languages is outlined in the task description: there is a text corpus in these languages (authored by Tolkien and some others), and some of it (e. g. first lines of poems and names of things) qualifiers for inclusion in Wikidata. I don’t see how the “completeness” of a language factors into this – Wikidata is not a place for original work anyways, so it shouldn’t matter whether I can produce my own texts in these languages or not.
Artificial languages are not what we support by default. I am not in favour
for these particular cult languages. I will ask the language committee if
they see it any different.The fact that Tolkien wrote some poems is in
itself not enough.