I am also not a mathematician, but I think this is an assumption that people are making. It could be that by reading the solutions/proofs of these AI-generated results, those methods could still be discovered, ie. the AI could be discovering new novel methods implicitly. It's not exactly the same thing, but when the Navier Stokes blow-up "solution" came out, there was a lot of hoopla around it being stolen and not novel, but then once the dust settled, we had this:

> But closer examination reveals that OpenAI’s proof builds its unnatural force in a totally distinct way. The proof’s similarities to Buckmaster and Alpöge’s progress are superficial...

https://www.scientificamerican.com/article/openais-blockbust...

So I think more time needs to pass before a call can be made.

An interesting thought experiment is this: if we were to go back in time 150 years and tell our ancestors that Newton is just an approximation and give them a 5,000 page book about Special and General Relativity, QM and QFT, would we be robbing them? Initially the whole thing would be incomprehensible, but eventually they would chew through it and make sense of it. I don't really know the answer (and perhaps the analogy is not great since we're quite attached to our physics heroes from the last 150 years).