Creep is caused by stretch, as the string stretchs the bracing height "creeps" down.
And tho yes I do use a non-creep material (BCY 8125) it wouldn't matter whether I did or not.
Bracing height is something that (theoretically) should be checked everytime you shoot so you know what it should be. And if its dropped you put more twists into the string. Therefore, even if the string has stretched you'll have enough twists in it that it will be the right length to set up the jig