On strings 123 and 456 the triad grip number lines up with the location of the root. Ie on 123 triad grip 1 for the major and minor grip the root is on string 1. For 456 grips triad grip 1 the root is the 1st string of the string group (4). Grips 2 and 3 for major minor grips the root lines up with the grip number.
This makes it easier for memorization (for me anyways). On strings 234 and 345 the grip number does not line up with the location of the root note.
Just wondering if this is coincidence or is there a reason for the order as presented in the material?
The root notes line up in the order of the chord shape they are taken from. The 3 chords mostly used are C A and E. C chord shape the root notes are on the A and B, the A chors shape the root notes are on the A and G and the E shape chord the root notes are on the E, D and e. If you know these shapes you can play most of the triads.
It’s how a guitar is laid out and what the CAGED system works. For everything not just triads. There really isn’t a grip 1 2 or 3 these are all chord fragments.
Justins numbering of the triads Grip1,2,3, is I believe, incidental, perhaps as a means of initial memorisation; not sure what his rationale was, but its not intrinsic to any musical structure. I didnt notice it tbh when I first started learning them. If it helps you to get the roots initially ingrained, then all is good.
You’ll notice that when you take a triad horizontally along the fretboard ( different positions) , or vertically up the stringsets (same position), its an endlessly repeating ‘conveyer belt’ of triads in root, first, second inversion, root, first, second inversion etc, wherever you start, in whatever key.
Reminds me of one of those kids toys that rolls over on itself as it climbs up and down the stairs.