It is actually pleated to the Stripe. If you look at each pleat there is a stripe down the center of each one.
It's interesting that they were able to almost imitate the Sett while pleating to the Stripe. Kinda cool concept.

If this were pleated to the Sett the ratio of the Sizes of the elements of the Tartan pattern should be the same front and back.
As ChattanCat says you can't always make it perfect but at least the ratios should be the same.
Also, if pleating to the Sett all of the elements of the Sett should still be present even if the overall Sett is squished or stretched a by 1 or 2%.


Pleating this way breaks some of the rules though. The prominent stripe used for the center of the outer apron should be centered in the back too.

I also think that the back looks sort of busy. That may only be the Tartan so I will have to look at and experiment with some other Tartans and see what a different Tartan would look like