Without experimental data to back it up (e.g. implementation and benchmarks), I'd consider this claim veeeery dubious - regardless of who it came from.
Extraordinary claims need extraordinary evidence, and in this case it would be easy to provide such evidence - by cracking appropriately-sized challenge primes in a transparent way that can be independently verified.
On the other hand, the theoretical approach in the paper is quite complex and hard to follow - even for professional cryptographers.
There are some approaches that seem difficult to implement at first view, but that can be improved when more people work on the difficult pieces. The most important thing in a paper like this is the general strategy. Even if there are small issues or if the implementation is too complex, if the general ideas are right we can find a better way to solve these problems over time.
Depends of the claim.
For the theoretical result, the evidence is the paper. (I have no clue whether it’s correct.) Nothing else is needed.
For “RSA is broken”, it depends what broken means. If it would rely on a claim that is now provably false, it is indeed broken. If we are talking about the claim of breaking RSA in the real world, I agree with you. But it all depends on the claim.
"This giant prime number will keep your information totally unreadable to anyone who doesn't have this other giant prime number" is no less of an extraordinary claim, just one that we all believe in (myself included).
Extraordinary claims need extraordinary evidence, and in this case it would be easy to provide such evidence - by cracking appropriately-sized challenge primes in a transparent way that can be independently verified.
On the other hand, the theoretical approach in the paper is quite complex and hard to follow - even for professional cryptographers.