Yeah I don't know how to access the Creators Collection outside of an Xbox One, altho you can search for individual games in the PC Windows Store. And even within the XBox One, it's small and easy to miss.
Crystal Brawl is completely free. In the 2 months that it's been out on Xbox One, it has almost 20k installs, 7k were in the first week of the announcement. And I see some other free games have many more ratings and reviews than ours, which probably means they have many more downloads too. But I see some paid games that don't even have any ratings. I'm going to guess sales aren't amazing, but it sure would be nice to get some numbers.