I suppose the point is that even though any given instance of an error like this is overwhelmingly likely to be an innocent mistake, there is some significant p

I suppose the point is that even though any given instance of an error like this is overwhelmingly likely to be an innocent mistake, there is some significant probability that one or two such instances were introduced deliberately with plausible deniability. Although this amounts to little more than the claim that "sneaky people might be doing shady things, for all we know", which is true in most walks of life.