Yes, ratio math works without the strangeness. Except it's unfortunate that the 3rd harmonic is the fifth letter and the 5th harmonic is the third letter. Coincidentally, from harmonics 7 through 14, the harmonic numbers match the letter-count numbers. That's partly because 7:8 is the beginning of the harmonics being roughly whole-step sized, and 14:15 is where they shift into half-step size.