I had to read that article (sales pitch) again. It can not possibly be referring to vintage Thurries and Eschers. I have not tried a 'new' type, but from what I have heard they are inferior to the vintage variety and therefore may be sub par to a coticule; however even if this were the case I do not agree with the rationale for it in that garnet systems (of coticules) and the quartz system (of mud stones ie. Thurries) are incompatible. This simply does not make sense.
Finer abrasives are finer abrasives, regardless of their origins. Out of the 5 coticules that I have owned, all except for one were inferior to either of my Eschers and my vintage Thurry. I kept one coticule which maybe just slightly ever so slightly below the finish of my Eschers.
Bottom line: for me a coticule's edge is ALWAYS improved by an Escher.