I believe that is in line with their findings. Since Japanese has more syllables than any other tested language (where nearly every other letter is a vowel) it would make sense that a faster rate of unknown syllables flying by would result in the perception of faster speech.
It's interesting that while the Japanese have such a focus on efficiency, their spoken and written language is potentially more contrary to this value than any other language out there.
It's interesting that while the Japanese have such a focus on efficiency, their spoken and written language is potentially more contrary to this value than any other language out there.