While studying workbench designs I read a 2007 article by Chris Schwarz in Woodworking Magazine about the Holtzapffel workbench. He describes it roughly as an eclectic bench with French, German and English influences.
Although the article mentions a tool tray and tail vise, Schwarz proceeds to build a Holtzapffel bench without them. The result looks a lot like a Roubo to me, except with a twin screw instead of a leg vise.
This made me wonder what exactly makes a bench a Holtzapffel instead of a Roubo. Is it just the vise, or is there more to it?
Please appreciate that my question is out of theoretical interest and not from any practical need. I can build a fine bench without worrying about the historical origins of the design.