On a left chest, distortion is a rounding error. On a 14-inch jacket back it compounds: every zone you stitch pulls the fabric under the zones you have not stitched yet.
By the time a poorly planned back reaches its final color, the registration has drifted far enough to see from across the room. Lettering that started straight is bowed, and outlines no longer meet their fills.
Large backs also carry serious stitch counts, so sequencing decides whether the job makes money. That is why every file comes with a stitch count and run time; you can check your own figures in the free stitch count estimator before you quote.
If the first color of a back looks perfect and the last one is visibly off, the file was stitched in artwork order instead of being sequenced for the fabric.