The M3 is good not only for the symmetry it provides when moving horizontally across string groups but also for the symmetry it provides when moving vertically up the fretboard. Horizontally patterns repeat for every three strings, and vertically patterns repeat for every four frets. The table below illustrates how you might want to play a C pentatonic scale by using the notes in an area that spans four frets vertically. You can then allocate one fret to each of your left hand fingers (many of the Single-Note Runs are constructed like that). The C notes are indicated by hollow dots, and the pentatonic scale is mapped out on the fretboard with the open strings at the top.
| 0th position | 1st position | 2nd position | 3rd position | 4th position |
|---|---|---|---|---|
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Notice that when you move up the fretboard one fret at the time then after four shifts of position you arrive at the one you started with, except it is now translated down one string. The highlighted area in the 0th position looks the same as the highlighted area in the 4th position. Generalising from this example, it means that no matter what scale you come up with it always exists in four positions on the M3, and those positions are right next to each other! You are never more than two frets away from your favourite position! If you want to, you can anchor your left hand at, say, 5th fret, and play all your favourite licks without having to anchor your left hand below the 3rd fret or above the 6th fret (or, equivalently, without having to anchor your left hand below the 4th fret or above the 7th fret). Contrast this with the conventional tuning where nothing repeats vertically within an octave, and therefore the positions you have to practice are spread out over 12 frets.
In practice, too much position playing is limiting, and I advice against making a habit out of always playing within a narrow range of frets. The point is that the vertical symmetry works in your favour in terms of logic, and it enables you to shift up and down the fretboard knowing that you won't land in a position you are not familiar with.
Be aware that large intervals require you to skip across strings more often on the M3 than in conventional tuning, and you also have to shift up vertically more frequently in order to get to the high notes since the M3 has four semitones less in the top.