He doesn't say nothing was really proven - he just says that they didn't establish whether this dislike of dissonance was innate or not. That wasn't what the experiment was about. It was to find what caused the dislike - and they ruled out 'beating' and propose it's harmonicity.
It's also not beating per se which people find unpleasant but rapid beating -roughness. Does Gamelan try to produce 'roughness'-ie rapid beating - or just beating - which I could imagine would be quite cool.
Fair enough, and I shouldn't just knock it without even reading carefully. It's frustrating sometimes to see discussions like these that seem to completely ignore the very wide variety of sounds that people find pleasant. I've perhaps read too many claims that "music is a universal language" when it far from that.
You should search out some recordings; I played in a gamelan ensemble for a while and quite enjoyed it. The sound is cool, and the interlocking rhythms do neat things in your head. :)
The beats -- I'm not sure if they're rapid enough to qualify as "roughness" or not; I've never encountered that term before, but they're fairly rapid and give a shimmering effect.
