Firstly I respect Wilhelms objectivity and acumen and in no way suspect the company is bending results to present client products in a better light. It is a fact , though, that cross company products eg Epson printers with Cone inks or /and Crane paper are seldom, if ever tested. From their point of view this makes perfect sense. In the real world, that does this sort of thing, it is frustrating that we have no one to turn to to provide the information that our clients- museums, galleries and artists, often request.
There is an issue the Wilhelm is completely open about, but is of some concern with critical clients such as museums, and that is the extrapolated cut off point of about 30% loss in colour density. The trained human eye can detect much less than this .
In any case figures are only comparative guides. A pale image containing high proportions of light magenta and light cyan will fade faster than a dark or saturated one containing relatively more of the denser inks.
As far as the optical brighteners go , I will endeavour to source some research as my information is largely anecdotal. I have obseved , however a yellowing in the whites, particularly on very white photo type papers, one matte art paper and a canvas.The yellowing appears where prints are exposed to fairly high UV light (inside , but near a large window).Similarly unframed prints in a plan drawer, that is exposed to atmosphere but not light , have not exhibited the phenomenon. In any case we are 2 km from the nearest lightly used road and 30 km from the outskirts of town , surrounded by a National Park. Pollution is not a problem. I would not name the products without much more rigorous testing, but can only advise you get what you pay for.