I vaguely remember looking into this before, and it turned out that the tasters were being told (incorrectly) that it was a red wine, and asked to describe the flavour profile. They then used tasting terms more frequently associated with reds than with whites, and didn't question what they were told.

So it's less a case of "they cannot distinguish red from white" and more a case of "they went along with a suggested classification". I feel like this is a weaker result, although it's still a little surprising.