Most likely because they submitted almost immediately after the jam started with a game released on itch.io a couple days before the jam started. (Truth be told, the game was also released on Gamejolt about 21 days ago, so it was finished even before the themes were up for voting. And if we really want to be pedantic, one of the screenshots clearly indicate that their submission is 18+ and contains violence and extreme profanity, which would most likely go against the "no NSFW" rule if true.)
It's possible they hit the submit button early with a pre-existing game to cement themselves as an entrant, misunderstood that a gamejam entry is supposed to be developed during the jam time, or misclicked and accidentally submitted with the game they did. It's just... not a great look if it is that, especially since their post insinuates that they're in the process of making the game.
That said, I don't know why you got downvoted for that.