Are they actually producing new math? In the most recent ACM issue there was an article about testing AI against a math bench that was privately built by mathematicians, and what they found is that even though AI can solve some problems, it never truly has come up with something novel and new in mathematics, it is just good at drawing connections between existing research and putting a spin on it.
It's finding constructions and counterexamples. That's different from finding new proof techniques, but still extremely useful, and still gives way to novel findings.
I'm not accusing you in particular, but I feel like there's a lot of circular reasoning around this point. Something like: AI can't discover "new math" -> AI discovers something -> since it was discovered by AI it must not be "new math" -> AI can't discover "new math"
For example, there was a recent post here about GPT-5.4 (and later some other models) solving a FrontierMath open problem: https://news.ycombinator.com/item?id=47497757
That would definitely be considered "new math" if a human did it, but since it was AI people aren't so sure.