Its shown even if i check "hide all DLC" in store.

The same happens for "The Chronicles Of Myrtana: Archolos". I contacted GOG's support about that, and they said it's because although the main game is required for someone to buy it for free, it is not DLC, but a standalone game. I suppose that makes some sense then.

I see Free Characters Bundle isn't listed as DLC, but I think it should be. It doesn't sound like a standalone game at least.