> If you're a senior developer, you're the one who has to push back against behaviour you don't like. You have the authority. "Hm, interesting question. I'm going to need more context before I can give you my point of view. Can you give me a quick overview of the system architecture / explain what actual problems you're trying to solve with this approach?"

One of us misunderstood the GP; I understood him to mean that, because he did not write the code, he was not able to answer the questions based on that code.

You seem to think he meant that he could not answer questions on someone else's code.