Since Capcom kept Hugh's Scribble Suit exclusive to the Sketchbook demo and made me port it myself to the full game. I wanted to make a trivia post about it since it is an unlockable that I and many others have become quite fond of.
The Scribble Suit is not that much different from the original Delphi Suit. The scribble decals are just extra materials added to the original Delphi Suit model (labeled in the screenshot as ch0012_00_Paint). Capcom also made copies and edits for those copies to the existing materials of the Delphi Suit for the scribble decal materials which I think is a cool and unique way to approach how they made it work without needing to edit existing textures.
After finishing the game, I knew the Scribble Suit didn't exist at all when I couldn't find the folder but also when I tried to find its material shader which also just doesn't exist. All of that is exclusive to demo and I had to include it with my mod for it to work in the full game.
So why didn't Capcom include it in the full game? Idk, and it really sucks that it's exclusive to the demo and probably will be forever. Unless they have a plan to include it in an update for celebrating its success. It remains exclusive to the Sketchbook demo.