No- he's saying that some people who have the intellectual horsepower to pursue it choose to pursue other things instead.

Unless I misread, I don't believe I saw anything that implied that the poster was claiming that anyone with a modicum of smarts could contribute significantly to the study of elliptic curves as relates to Diophantine equations. That being said, there are a mind-boggling number of extremely specific sub-specialties in mathematics, each of which would demand a significant investment of time from even a very intelligent person to reach a deep understanding of the state of the art. The fact that only a handful of folks are sufficiently versed in a particular sub-specialty to evaluate a long, involved and presumably brilliant proof attempt that draws significantly upon the state of the art of that sub-specialty does not imply that only a handful of folks are sufficiently intelligent to evaluate the proof. This reminds me of the recent attempt on the P/NP problem by Vinay Deolalikar - plenty of extremely talented mathematicians watched from the sidelines because they did not have sufficient specialized knowledge to properly evaluate the proof; though, that did not imply that the proof was particularly brilliant or even correct (http://michaelnielsen.org/polymath1/index.php?title=Deolalik...).

Reputation in the field is not a proxy for general intelligence. That there are only 10 people with the reputation to make it worth them assessing the proof does not mean those are the only 10 people with the smarts to understand it.

And yes, a large part of being able to work in a specialized field like this really is about having the specialized knowledge and vocabulary, rather than general intelligence. If this is anything like most proofs in mathematics, most reasonably intelligent people would be able to understand it given ten years of studying the field. It's not about being smart enough, there's just so much existing knowledge that you need a lot of specialization to be able to really contribute to any given area.

It is not unreasonable to assert that it takes intelligence to understand this area of mathematics. However, it is wholly inane to assert that one is intelligent if and only if one understands the intricacies of this proof.