Apple has rolled out a change to the Apple TV App Store that will make it easier to find new apps. A number of areas of the store will no longer display apps that you already have installed. While this change is most notable in the top app charts, we've also observed it on the App Store's front page.
As noted by 9to5Mac, you can try this for yourself by downloading any app from the store, then force quitting the store app, and reloading it. If you downloaded an app from the top charts, you should notice that it has been replaced on the charts with the app that was directly behind it in the rankings.
This is a nice little change that could help Apple TV owners explore apps that they might not have otherwise seen. No word yet on if this change will come to the App Stores on iPhone, iPad, and Mac.