If the seams are sewn with sewing thread, they are not a good choice for unravelling. Those seams have been serged, and the fabric is trimmed along the side as it is stitched. So, if you pull it apart, you will just get lots of yarn strands which are not very long. Now you have experience on your side, and know how to avoid those.
All yarn is curly when you unravel it. I usually wind it on a swift, or around a chairback, gently add some securing ties all around the hank, then get it wet, and gently squeeze it dry in a rolled up towel, then hang it to dry, with some weight pulling it straight. (Not too heavy, to avoid stretching) This pulls out the kinks, and it looks like new yarn.