This isn't about being AGI or not, and it's not "out of thin air".

Modern implementations of LLMs can "do research" by performing searches (whose results are fed into the context), or in many code editors/plugins, the editor will index the project codebase/docs and feed relevant parts into the context.

My guess is they either were using the LLM from a code editor, or one of the many LLMs that do web searches automatically (ie. all of the popular ones).

They are answering non-stackoverflow questions every day, already.