Matt,

Yes, the twelve-and-a-half yard monster I suggested is just a hypothetical example. (Wouldn't that be fun to make? ) Anyone who wanted a kilt pleated to the sett using such a large pattern (like Black Watch) would realistically have to settle for one of two options:

1) Fewer pleats (say fifteen or seventeen) with a wider reveal but uniform depth throughout the kilt.

2) "Cheating the Pleats". This would be used to maintain the high number of pleats (27) I suggested in my example. However, some elements in the tartan don't repeat themselves so there would not be a uniformity of pleat depth. Every few pleats would require using the full repeat of the sett. Sure, this would drastically reduce the kilt's overall yardage from the aforementioned twelve-and-a-half yards, but you would still need about eight yards to accomplish this. Eight yards is still a lot more than six-and-a-half, especially when dealing with many kilts being made from the same bolt of tartan.

The army is nothing if not frugal and in situations like the Great War, where there was a high 'turnover' of kilts, economy of cloth would become an issue fairly quickly. Almost every detail of a military kilt indicates economy of cloth: no apron fringe, small apron facings, non-tartan waistbands and buckle tabs. (The latter two also make alteration easier.)

Yes, I've made traditional box-pleated and low-yardage knife-pleated kilts to the sett as well, but I'm referring to military kilts that 'require' a high number of pleats. So I still maintain that it was done for both tradition and economics.