Probably for one of the reasons graphql was created in the first place - accomplish a set of fairly complex operations using one rather than a multitude of API calls. The set can be "everything" or it can be "this well-defined subset".

You could be right, but that's really just "Our API makes multiple calls to itself in the background"

I could be wrong but I thought GraphQL's point of difference from a blind proxy was that it was flexible.

It is flexible, but you don’t have to let it be infinitely flexible. There’s no practical use case for that. (Well, until LLMs, perhaps!)

I guess that I'm reading your initial post a little more strictly than you're meaning

I think they mean something like (or what I think of as) “RPC calls, but with the flexibility to select a granular subset of the result based on one or more schemas”. This is how I’ve used graphql in the past at least.