According to Itch the game was "published" 13 days ago (from today the 15th, this game jam started on the 1st which means the game was published on the 2nd giving him a development time of 1 day.
The rules do not state you cannot submit to other game jams or develop for other games jams initially, only that you must start development at the start of this game jam to submit.
So question is, did he create that game in 1 day?
(I personally don't mind if Night Light or Little Knight ( currently in 2nd) wins, I only want it to be fair)