It depends a lot about the ratios here. There's a fast flip between "interesting but useless" and "useful" when the tradeoff flips.
How fast can you check the contribution? How small of a part is it? An unsolicited contribution is different from one you immediately directed. Do you need to reply? How fast are followups? Multi-day back and forths are a pain, a fast directed chat is different. You don't have to worry about being rude to an LLM.
Then it comes down to how smart a frontier model is vs the people who write to mathematicians. The latter groups will be filled with both smart helpful people and cranks.
How fast can you check the contribution? How small of a part is it? An unsolicited contribution is different from one you immediately directed. Do you need to reply? How fast are followups? Multi-day back and forths are a pain, a fast directed chat is different. You don't have to worry about being rude to an LLM.
Then it comes down to how smart a frontier model is vs the people who write to mathematicians. The latter groups will be filled with both smart helpful people and cranks.