Exactly this. If you take the entire start to finish 'agent hours' (measured comparably to man hours) they took to find all discoveries, including the go-nowhere trails that were discarded, and then divide by 90 (or whatever the exact number of results found was) it's almost certainly going to be many orders of magnitude more than 3.

They provided a "snippet" of a prompt here [1] which is not only a beast, but also seems reasonably likely to have been LLM generated. So they're using LLMs to parse a vast body of mathematical work, probably including what people themselves are 'privately' working on with GPT, and then prompting other LLMs to work on such.

[1] - https://github.com/openai/math/blob/main/reasoning_traces/re...