Isn't it possible that this is only a part of a full die?
A full die shot has on all the sides a blue ribbon that states the division between the processors on a wafer for the cutting (I think). This die shot has only two sides with a ribben (top and right) seems to me that this is not the full die?

Compare that to a full die shot of istanbul.

Still doesn't explain the reasen why the different pieces are not the same size.