The idea this person is trying for is a LLM that explores the codebase using the source graph in the way a human might, by control+clicking in idea/vscode to go to definition, searching for usages of a function, etc. It actually does work, other systems use it as well, though they have the main agent performing the codebase walk rather than delegate to a "codebase walker" agent.
My concern would be that a function called setup() might mask some really important thing, likewise a “preface” chapter might get missed by an LLM when you ask some specially deep question.
Either way that your input data structure could build bad summaries that the LLM misses with.