They say a lot, but give no results that can be compared with other studies, and there is a lot of real data to be compared.

Experimental results on harmonizing, as recognized by the human ear, are given in a graph on p. 167 of the 3rd edition of Juan G Roederer's 'The Physics and Psychophysiics of Music', 1995. [See also his bibliography, where there's a lot of real data noted.]

What do any number of normal speach patern's of any miodern language have to do with speech capacities of the originators of music? They may have discovered harmonization by beating sticks or femurs on hollow logs of various diameters and lengths and material constants
before they had any language.