As far as I can tell, that article says that there have been no studies of the ergonomics of alternative layouts, in contrast to hardware changes, which are well-supported. It does say that dvorak and others were designed by people who knew about ergonomics.
http://www.sciencedirect.com/science/article/pii/S0169814198000997 should have it but is paywalled.
Luckily, some website called Common Sense Atheism made it available.
As far as I can tell, that article says that there have been no studies of the ergonomics of alternative layouts, in contrast to hardware changes, which are well-supported. It does say that dvorak and others were designed by people who knew about ergonomics.