Staple Fret Design

I'm really curious about the width of the staple frets in pre-revival dulcimers and what that might imply, if anything, about how these early instruments were played. L. Allen Smith often described dulcimers with "Two of three strings fretted on 15 frets." or even "Three (?) of 4 strings fretted on 15 frets". Beside the physical fret width relative to the strings, I assume he could also see the corresponding fret wear as well. Most discussions here, including Robin Clark's fascinating work with intonation and temperament assume fretting only one melody string or maybe one melody course. Does this suggest a little additional exploration of early playing styles or was there some other practical reason for making the frets wider, maybe for ease of installation if nothing else?