Mount Everest, as far as I know is near 8850 meters high, which in feet is probably around 30000. The article snippets you took seem right to me, the author math checks out.
I guess what I'm saying is the AI is showing better understanding of climbing context than the author is giving credit for.
It's far more likely that the program cobbled together a variety of factoids and so got it's wrong-sounding statement in the same way it makes many other clearly wrong or illogical statements.
It sounds like you're suggesting that if it could get the number right, it would probably also be able to model people well enough to understand they would consider it a mistake.
I'm not highly confident of its ability to do the former, but it has zero information on what sort of person is interacting with it, correct? I don't see how it can possibly know.
Whereas, it must have the fact embedded in it.
We don't have to reason with counter-factuals here. GPT-3 just reproduces language. It isn't trained to be right, it's trained to predict and reproduce language so it has no incentive to be right. And the pattern of saying something correct but wound-sounding is quire rare in my experience. Most people who do that do it by accident as well I think.
It also has no model of people and it knows no numbers. Everything it spits out is response to context, which does allow to seem to model people and seem to know numbers.
No doubt, it has an association with some article describing the actual distance of an Everest ascent as well many other facts and misinformation about Everest. It will spit all this out in context.