The reason this distinction matters is because I think its important to understand that not only European musical traditions will have equivalent rhythmic complexity but also other musical traditions will have equivalent harmonic complexity. Just because we don't have a great model of other musical traditions' harmony, does not mean they lack harmony. And vice versa. E.g. during Baroque era although temporal information was rarely denoted on paper (any more than 3 time, 4 time, tempo etc) musicians performing these pieces had to express a certain understanding of rhythm. Pieces were never played like MIDI, they always had rhythmic nuances.