[cjslep]

GP is talking about things like the chromatic scale, pentatonic scale, whole-tone scale, etc

Writing melodies with these would comprise of 12, 5, and 6 different tones per octave, respectively. Not 8.

Plus, some minor keys comprise of different sets of tones depending whether the previous tone was higher and lower, so it might not even be the same set of 8 tones within an "8-tone" scale.

Octaves are just a modulus.

Edit: there's also things like moveable 7 note "scales" and other eastern hemisphere things that don't fit western music theory as easily but I don't know them well enough.