Well, I believe the manual mentions it, and even if we are to discredit the manual, the classes on the lower branch have a clearly more "evil" theming to themselves: Death Hand's name and weapons (Skull Dissect) also the way the Duelist dresses, the fact Fenrir is the god devouring wolf during ragnarok and so on.
In any case, allow me to try to explain the table.
Let me use Duran as an example that follows the correct order that you pointed out.
The table data structure is as follows:
Class family is a value from 00 to 05, with 00 being the Fighter classes, 01 being the Grappler classes, and so on.
Class changes is 00 for the base class, 01 for a second-level class, and 02 for a third-level class.
Light-dark scale can range between 00 and 03, with 00 being light-light and 03 being dark-dark.
Fighter 00-00-00 Fighter
Fighter 00-01-00 Knight 3-step cut
Fighter 00-01-01 Gladiator Whirlwind Sword
Fighter 00-02-00 Paladin Flashing Sword
Fighter 00-02-01 Lord Magic Circle
Fighter 00-02-02 Swordmaster Vacuum Blade
Fighter 00-02-03 Duelist Eruption Sword
This is Duran's table. Notice how dark class branches increment the last value with each class change (even if you don't care for the name of the branches, please bear with me for the sake of argument). Dashes aren't present on the table, I just added them for legibility.
Now for Kevin here's what you have:
Grappler 01-00-00 Grappler
Grappler 01-01-00 Monk Whilwind Kick, Tornado Throw
Grappler 01-01-01 Bashkar Water-Moon Slice, Bastard Slam
Grappler 01-02-00 God Hand Byakko Shockwave, Stardust Bomb
Grappler 01-02-01 Warrior Monk Genbu 100 Kick, Blow Impact
Grappler 01-02-02 Dervish Suzaku Sky Dance, Veritubach (wrong translation, should be BTB, Belly to back, as in the throw move).
Grappler 01-02-03 Death Hand Seiryuu Death Fist, Dead Crush
The index of the first value went up by 1 because I assume Kevin is the second character in memory. Notice that to match Duran's table, Death Hand should be the last class of the "low" branch.
A few more points of interest: Dervish and Death Hand have their palettes wrong, they are swapped around when you compare them to the status screen art, which would make zero sense unless something was afoot. (I can try to supply screen shots of this if you'd like).
Also, at least in vanilla SD3, Death Hand is clearly stronger, while Dervish has more survivability due to HP sapping saber magic. In terms of raw damage though Death Hand wins out, which doesn't match up with any of the other characters.
I'm not trying to convince you, but I honestly think the developers made a mistake.