Greg Brockman says that arithmetic answers are readily verifiable, whereas proofs, particularly natural-language proofs, are much harder to verify.

“sense part of it is that you could think of it as that well mathematics is checkable but that's not quite true anymore right like we really started with very checkable problems of here's an arithmetic problem there's like some numeric answer and so you have an AI that you can train to just like check if it got the answer right because we can very much perceive is the answer that the AI is proposing the same as the actual answer but for a proof very different proofs are very hard to check is this”

“actually accurate or not formalized proof okay yes that is checkable but but natural language proof which is what we're really producing here much much more difficult but the thing that actually i think is the core insight is really about data right it's that you can get lots of data in mathematics you get lots of data in theoretical physics can you get lots of data in biology that's obviously something very data bottlenecked very difficult now fortunately we also have been working lots of techniques to be able to work with less data”