There are two choices when the time comes to arrange the pleats on your kilt - 'to the sett' or 'to the stripe'.
(there's a third choice: 'Total Bloody Chaos' - in which the cloth is pleated without reference to the tartan pattern, which I'm informed was how it was often done before the 1890s - but I've never heard of it being done in modern times)
I believe that you the client should have the maximum possible input as to how your kilt should look.
"To the sett' is straightforward, but if you choose to pleat it 'to the stripe' - which stripe shall we choose?
It seems that other kiltmakers will elect to choose for you - they'll pick the most-prominent stripe and pleat the kilt to that.