In result they don't seem to understand that the dvorak layout is optimized for alternation between hands (they do mention this) and inward rolling motion (they don't seem to understand this). You can really feel this when typing, and it makes typing downright enjoyable.
I wouldn't be surprised if much of the added distance relative to colemak and workman is probably reaching for the "i" with the left pointer finger. These are the easiest movements to make repeatedly, and in my experience the home row horizontal movement that they try to optimize out of workman isn't really important.
People should be free and encouraged to make their own layouts to beat RSI. But, scientific measurement of what is better seems basically impossible...