Most apps are one-offs so will be listed in books. We don't index enough apps to create an entire separate app tab for them. So far we have only indexed Baking With Dorie and Food52 Holiday Recipe & Survival Guide. You can easily find them by searching with App in the search terms box - you will get a few wrong books with app as an author or title but it's not many.
The Jamie Recipes App is something different. It acts like a magazine in that you subscribe and get updates. So we decided to treat it like a magazine so members can subscribe and have each new addition automatically added to their Bookshelf. Or if they only buy one or two issues then they can just add those individually to their Bookshelf in the same way they can with magazines.
What we will look at doing is create a separate Jamie apps option in the Quick Searches list on the right of the Magazines page and removing the apps from the Jamie Magazine listing.