Well, I frown upon it ;-)
It is as hechelion describe. It's just using Itch as a cheap hoster for promotion page. A parasitic activity. No benefit for Itch users, if they have to go elsewhere to play the game at all.
And I visisted the play.date site. Sideloading is even promoted by them. So I do not see the issue of having an offline version of an online leaderboard game. Peolple that want the leaderboard can go to the official site. People that just want to play the game, can play offline version.
If a game's merit is onyl the leaderboad, that does not sound like a fun game.