Boot manufacturers often change the location of the heel-lock on boots in the search for the optimal position.
The heel-lock helps keep your heel from sliding up and down and the rest of your foot from sliding back and forth in your boot causing discomfort.
In some cases, you might have to modify your lacing system to accommodate these changes.
Andrew boots reckon this is the best way to lace your heel lock; enter the lace from the top and exit the bottom of the heel-lock before returning to the other eyelets. This configuration offers excellent coverage and a more secure lock for your heel.