Sure, but I think that there was an implicit assumption that the person under consideration was explaining something within their area of expertise. Otherwise the article would be claiming that a smart person can explain anything simply, which amounts to equating "smart" with "omniscient".

The other assumption I made about the article was that it was discussing a useful heuristic, not a 100% reliable test. The inherent complexity of the world is one of the things that can make it give the wrong result, but not the only one.