Bundles or not, this is an essential feature for a site like itch.io. It's a storefront for so many different kinds of things; TRPGs, game assets, zines, video games for every platform. Even if they don't specifically buy bundles, long-term or spendthrift customers are going to have libraries stuffed to bursting with all sorts of stuff that they can't use right now; the ability to filter out those things would make the library so much more usable.
And itch does have that kind of filter! Just...not in the library. You can sort the entire storefront to only display pixel art strategy RPG roguelike deckbuilderss for Android, but you can't sort your own library to only display your video games? Ridiculous.