Hi, Silvain
All that was a good story but it does not relate to answer the necessity to designate scale steps (degrees) or notenames (in this case accidentals) with constant reference to major scale.
I am sure that those African and Asian and Polynesian had little (if any) knowledge or use of a... piano. I think you would agree that 5 tone (pentatonic) music existed for millennia before piano or harpsichord was even an idea. So the arrangement of the keys on a piano is irrelevant in this case. Also the reference to the major scale.
And if we look more openly (out of the box, so to speak) there is nothing that would make the harmonic minor more or less 'true' or 'identifiable' had we written its scale formula as:
1·2·b3·4·5·b6·7
or
0·2·3·5·7·8·11