You're using the idea of "all of human knowledge" differently in the two places it appears, and the gap in those definitions weakens the claim a bit.

LLMs are trained on a tiny subset of the written human knowledge which we've proven to probably not be garbage and which is nicely formatted in simple text formats and which was published without too many paywalls on the web and on and on and on. It's a lot, and it definitely includes enough facts that no one person knows all the things the LLM "knows", but the average child knows plenty of things which never made it into that sort of a corpus. Yes, it's probably true that the vast majority of humans are also not pushing the frontier of human knowledge forward, but the vast majority of humans are working with a slightly different (partially overlapping) set of information than what the LLMs see.