One of the first things I do when I get a length of fabric is to open it out on a table and look at both sides to see which is better, sometimes if you run your hand over the surface you can pick up any knots or slubs more easily. I then decide which is the better face, it's not always the same even from the same weaver, so as everyone has said as long as the best fabric face has been used on the outside I wouldn't worry about the twill direction. These days it is often very hard to tell the difference between the sides. So enjoy your kilt and wear it well, there is nothing wrong with it!