I have seen this happen with batik fabric a couple of times. I have a piece that has some distortion. In the process, as you know, wax is applied and then dye; the wax is removed with a heat process; new wax is applied and then dye. If the wax is overheated when it is being removed it can permanently stretch or shrink the base fabric. If you use the fabric as a backing you will have to just, at random, to allow the variations to be stitched down in the tiny pleats. If, on the other hand, you used it on the top as a whole cloth quilt, you would have opportunity for interesting design features. I think the fabric it stunningly beautiful. Various chemicals and heat can do permanent change to fabric.