The question you asked was whether the AIs could prove the thing "in a vacuum", without making any use of previous human work. "Close to being solved" is a statement about all the previous human work that mathematicians might have used to do it in five years.

I didn't mean that as "we need hyper-intelligence." I mean that going all the way from nothing to singular, dual, plural grammatical numbers attached to particular nouns to abstract one, two, three, many to zero, one, two, three... to rationals to... is a very long way.