Say you have a web app, an iOS app and an android app. And let’s say the model of the data that makes sense for the purposes being the UI for these apps is different from the model that’s used to persist data in the database. It means somewhere between the database and the UI template you’re going to be transforming from one model to another. What you don’t want to do is have the equivalent transformation implemented 3 times — once per app; instead you want to do this transform at or below the common interface that they call operate against, ie the GraphQL server.

In my experience it’s very uncommon for anything other than simple prototypes to not have at least some divergence between the UI model and the persistence model.