Quilt judges normally don't critique what is used for the back.
However, if the back is pieced there may be comments on the workmanship of the piecing and how it effects the overall stability of the quilt. Such as, if it is seamed in the center, is that seam straight with the edges of the quilt. Did that seam produce a bump that effects the visual effect of the front. Comments related to the back are usually related to other aspects of the quilt - pleats from quilting, loose strings, knots showing etc.