Hi @cloud84,
The chords triggered in those presets seem to be chosen based on the intended use as per the preset name.
So "Songwriter Left Hand" are just triadic voicings one would play with the left hand on a keyboard (?), while "Guitar Open Chords" are voicings that for the most part include notes that happen to be open string notes on guitar.
Also, a notable difference between the "Songwriter Left Hand" and "Guitar Open Chords" presets, is that the latter contains voicings that use 7ths and other harmonic extensions (6ths, 9ths, 11s, b13s).
As for the choice of chords to be triggered by D# in both presets, the only explanation I see is this:
Guitar Open Chords: D# is the major third of the B7 chord
Songwriter Left Hand: D# (enharmonic equivalent of Eb) is the minor third of C minor
Hope that helps?
J.