I haven't seen it before, Luke. My guess would be an error. I believe that the chips we see with assymmetrical edge spots are made with a cutting die that has all the insert slots present. To make a chip with only one insert, the chip maker actually uses inserts of the same color as the base chip for those he wants to disappear. I can't see it on my chip with one insert, but I've seen chips with other strange insert arrangements where some of the inserts are base chip color and you can make out the edges of the invisible insert.

I'd like to get one of the three-insert chips if you happen to have an extra.