For sure. Unrelated to GraphQL in this case. Very manual (in a good way!). Sometimes it's achieved manually via the UI. Sometimes manually via scripts, etc. Imagine you're creating a new field for Business Travel, and you've added some new fields via the API. One way or another you're grabbing 1-2 listings in development, modifying those listings to reflect the desired change, and then in the dev setup, you're saying "grab listings x and y and update their data for use in Storybook and unit tests."
In my experience, if the system is working properly, there's not a lot of room for type-driven inference. We often get a design with very explicit data present, and we want to bring that data in rather than calling on Casual or