You could make a purchased collection. A wishlist collection. A favorite purchased collection. And so on.
The purchases only look similar to your collections. It basically is just a history line of your purchases. I do not think it is intended to be able to sort or remove items from there.
But it would be nice to be able to "hide" it from library view. Or if you want to brag with your purchases, to select which ones do appear there and in which order. Right now there is only a button to show it or to not show it.
You could show a collection with purchases, but this does not prove you really did purchase the game.