Hmmm, having played guitar myself and created art both pencil and paper (33 years) and clay (1 month) I would say that your analogy is a little faulty. I had a student tell me he knew how to play the bass guitar because he had learned on the IPad, and I will admit it made some great sounds, but when I handed him a real axe he couldn't play a lick. Not a single note and he kept complaining his fingers were sore. Now a great guitar player could pick up the iPad and just kill it, but the inverse isn't always true. Now I do get that Rick Baker and Andy B can KILL a clay sculpt and then take that same knowledge and kill a zbrush piece. However, I don't necessarily think a Zbrush artist could do the same.
Speaking for myself after 33 years of creating the illusion of 3D muscles and form on paper (only getting fairly good in the last 10) there is something very different about holding a lump of clay in my hands, and trying to actually make those same 3D forms I have been studying for the last 33 years come to life so to speak. Honestly, if you haven't done it I can't really explain it other than to say it is a wholy different way of creating something when you can actually feel it in your hands and watch it form with tools. Now, I get that the masters are simply using a tool that is available to them... Most likely a Wacom Cintique tablet... And I don't blame them as they may have to make multiple variations on a design, and it is a hell of a lot easier to hit CTL +C than to brake out the armature wire and Sculpey. However, seeing Steve S scrapping off the clay from his Godzilla Maq, and build it up scale by scale... Well that was damn impressive....lol
P.S. for all we know these are cleaned up 3D scans of pieces he did in wax or clay, and then scanned.