As the article itself points out: there are judges. Therefore championship tallies as proof that an athlete in a niche sport is the greatest athlete ever must be taken with a huge block of salt.
True. I think with Slater though, even when he was 'retired' for a bit, he was still the standout in his sport. To be the single dominate athlete in your sport for two consecutive decades, is quite a rare feat.
But yeah, niche sport, shifting judging criteria, etc etc makes it difficult to compare with mainstream athletes.
I've forever argued with my friends that NBA players were the worlds greatest athletes (genetic lottery winners, marathon seasons, speed/agility/reaction, etc etc) but I thought this article was kind of thought provoking from a 'length of time at the top' standpoint.