Ganache be it white or not is less sweet than any butter icing. And that's why it cuts through the sweetness of the fondant. I hate fondant alone. And it was one of the reasons I refused to touch fondant for so long when it comes to decorating. But I love ganache with fondant. I also prefer a meringue buttercream over basic buttercream for the same reason. It's not as sweet and has zero graininess. I'm a textural weirdo lol.

Also try not to dust the top of the ganache (only the underside) or this can result in dry cracked or rippled fondant.