No one ever told me my quilt had to be the exact same on each two sides. It wouldn't have mattered to me if they did anyway. LOL
A 1/2" was acceptable even with the well known teachers I have taken classed from.
If adding a border it has been drilled into every quilter to take measurement across and down and then average the difference if any both ways. After quilting the quilt will be
squared up (cut the excess backing and binding off) by the quilter or yourself and then add the amount of binding you need to go around it.