You would have to ask the builder.

I suspect a longer wheelbase, the seat and head tube angles, and fork rake were key attributes. I doubt that the frame material (magnesium) was a factor. Ability to mount somewhat larger width tires is a big factor because wider lower pressure tires make descending bumpy roads easier. I do notice that the chain stays are longer than all my other bikes except the circa 1986 Klein touring bike up in the attic. The top and downtubes seem really beefy. SOrry not to be more helpful