It definitely requires more work. If you're starting from scratch, you need to either read the API documentation or makes calls to the API to understand the data you're getting back. You then need to build correctly typed data models that match what you're expecting the API to give you. There's plenty of room to make mistakes as it's a manual process.
With GraphQL you can take the schema file from the server and use it to generate your data models. You get the data models for free, everything is correctly typed, and as long as the schema you're using is up to date you have a guarantee on correctness. It also makes finding changes to the schema easier in the future, as you can effectively do a diff.
We also use GraphQL on web (the exact same API as mobile) but we don't realise nearly as many of these benefits. This is probably in part because we haven't invested a lot in tooling, but also the team that maintains the API also maintains the web product, so some of the discoverability benefits of Graph aren't as valuable.
With GraphQL you can take the schema file from the server and use it to generate your data models. You get the data models for free, everything is correctly typed, and as long as the schema you're using is up to date you have a guarantee on correctness. It also makes finding changes to the schema easier in the future, as you can effectively do a diff.
We also use GraphQL on web (the exact same API as mobile) but we don't realise nearly as many of these benefits. This is probably in part because we haven't invested a lot in tooling, but also the team that maintains the API also maintains the web product, so some of the discoverability benefits of Graph aren't as valuable.