Your method captures the two variable intervals, being either 3 or 4 semitones, between the three digits/fingers of the triad/chord. That is, you capture the essence of a basic chord.

The four triads can also be shown using whole numbers, representing the starting note 0, and the number of semitones to be jumped.

0 3 3 = mm = diminished triad
0 3 4 = mM = minor triad
0 4 3 = Mm = major triad
0 4 4 = MM = augmented triad

Both methods apply to any of the twelve notes of the octave.

As you mention, noodhoog, you can add a fourth digit to the triad, with a variable third interval, to create four digit chords.

0 4 3 3 = Mmm = M7 = Major 7th

This method allows for more digits, and intervals other than m = 3 or M = 4. All chords can be described this way.

Ex. C E G C = 0 4 3 5 = C Major = any 'complete' major chord, repeating the root.

The twelve-semitone interval method can describe the whole of music theory, which is currently organized around the seven notes of the major scale.

I would like to present the octave as the unit of organization for music theory on Steemit. In short posts of my own.