The Pokemon Company would be handling something like this I imagine. IIRC, they're usually far more aggressive than Nintendo when it comes to IP and roms.
I'm legit surprised anyone would create a site featuring Pokemon roms or hosting Pokemon fan games. That seems like a Bat-signal call to TPC. Seems the best bet there would be for creators to release their games, hosting download links for a while, eventually other sites pick it up and host it. Some get C&D'ed but not all, and if they do, then torrents.
But I'm not familiar with the site or situation, so what do I know.