yes, there is information in the answer of "No Time To Play".
In short, if you don't get enough attention to your game (people following the game via links), the game will not be indexed (The post say that you will not be given priority when it comes to having your game reviewed. But seeing that my game was indexed after I posted here, I guess that's not the whole truth.)
i wonder how itch really handle the support email and the indexation of games.