As far as I can remember, an early issue of StarLog (maybe issue 4 or 5) also played it up as though Trek's Arena was directly inspired by the Brown short story. Not claiming that was reality, just that StarLog reported it that way. That claim prologued a reprint of the original Brown story and even had a painting by Boris Vallejo depicting the defenseless astronaut and his alien opponent. A couple of issues later StarLog printed a letter from an irate reader stating, "I thought I had accidentally picked up an issue of PlayGirl!" Boris' painting depicted nothing more than the side of the astronaut's hip. Any "crack" was hidden by shadow and soil.
If Coon wrote the script before he know of its subconscious source, it would be interesting to know what he had originally titled his script.
Also, the old Starlog
issue (Number 4) with "Arena" in it can be found here:
Vallejo's pictures from the article are below. (I guess I understand the Playgirl
assertion; it's not really "nothing more than the astronaut's hip.")