I found this out by fooling around with a harp and discussing harp versus guitar plucking with a harpist.
To wit, the guitar right hand thumb has the most powerful arc of the two instruments. So guitarists often use the thumb to accent and add stress. Likewise the pinching motion of the thumb and the first two fingers are quite powerful.
The harp on the other hand, has strong finger arcs and weaker thumb arcs, so they even out.
Just something useful to remember when you transcribe harp music for the guitar, or guitar music for the harp, or write a guitar and harp duet.