I'm not persuaded there's an avoidance of translating GraphQL. Rather, I think it's largely because of a lack of awareness of that as an option. Most or all of the material written on the subject exclusively presents execution as matter of nested resolvers and that's how pretty much all the libraries work, so I think it's natural to assume that's the only way to do it.

I will say that translating to SQL does remove a convenient arena in which to write business logic in a general purpose programming language, which generates resistance to the idea of translation once it's encountered. But, as the author says, that mixes business logic with data marshalling code anyway.