I agree with Rocky that weaving tartan this way would not help at all with the asymmetric problem. I have, over the course of my kilt making career, encountered some lengths of cloth woven this way. To my recollection, they were all older lengths, purchased off of ebay or sent to me from a client for CMT work. Never from one of the mills currently operating within Scotland which I order from.

It doesn't really affect the kilt making one bit. Just surprising if you don't know what you are looking at.