I definitely agree with what you say, Robert. There is a very important distinction between a chip with an error in the artwork, design, etc., where a batch of chips were made that way, and an error that occurs during the manufacturing process rendering a stray chip unlike all the others. The second case is most generally likely to be a small percentage, unless the manufacturing process is REALLY bad [g].

With the first case, I would prefer to call the chip itself a variety. Ultimately, the "error" aspect only becomes significant if it leads to intentional scarcity, such as the chip never being used, or pulled and destroyed. Otherwise, it's simply an interesting characteristic, a bit of trivia, such as with the halloween chip.