> what the mathematically average chronically online person knows and thinks about a topic

Yes you do, often. Understanding ideas and consensus is part of understanding "topics". To choose a Godwinized existence proof: an LLM that didn't understand public opinion in, say, 1920's Germany is one that can't answer the question of how the war started.

You're making two mistakes here: one is that you're assuming that "facts" exist as a separate idea from "discourse". And the second is that you appear to think LLMs merely "average" the stuff they read instead of absorbing controversies and discourse on their own terms. The first I can't really help you with, but the second you can disabuse yourself of on your own just by pulling up a GPT chat and talking to it.