I noticed that Championship Riven, Pax Sivir, and Urf the Manatee all have their borders in the collection--makes sense, given that there are two versions of each of those skins and one version has the border. But today I noticed both Elementalist Lux and Gun Goddess Miss Fortune have their borders in Collection. If this is being done with every skin (I don't have any other borders), I'm all for it. It's a very nice feature to have.
Although now I'm even more bummed out I didn't get the border for my main champ, haha.