If anyone is still concerned about this, I suggest springing for a 2oz can and conducting your own experiments.
Not an expert by any means, I do believe that pressed plug, and crumble cakes have a distinct disadvantage to visual scrutiny, since their skin color can be compared to the much darker interior. Whereas, a rubbed tobacco will always appear uniform through even an extended ageing process of chemical changes.
My personal aversion to the ghosty, whitish skin color was eliminated, when after the reassuring e-mail arrived, I rubbed-out the remainder in the tins and enjoyed.
Who knows how much yeast or mold everyone has already consumed (and savored) from their prized "culture-jar" collection?