I'm not having the same positive experience on a >25yo insanely large and codebase built with questionable engineering practices

Or is it just giving you a limited understanding but pretending it's grokked the entire codebase AND data?

Yeah I've run several SOTA tools on our gnarly legacy codebase(because I desperately need help), and the results are very disappointing. I think you can only evaluate how well a tool understands a codebase if you already know it well enough to not need it. This makes me hesitant to use it in any situation where I do need it.

But that's already way better than a physical rubber duck. That was my point.