The reason it is
Machine Doubling it that the devices are incuse on the die. Lightest looseness of the machine will show the largest appearance of MD. The
DDR's on this design is on the centers of the devices.
Never on the outside edge devices. The single squeeze dies doubled dies are different than the multi hub dies of the past. Take a look of the doubled dies for that date/series and see what to look for and where to find them.