Judges at quilt shows look for binding that is full and that is the same amount showing on front and back. They may be able to do that because they are familiar with the weight of the fabric and batting they are using and know it will work. To me that is poor teaching if they do not share that principle. Others may not be aware of it and/or just do not feel it is as important. I use Quilters Dream batting for my personal projects...either their cotton select weight or their Dream Orient (my favorite, a blend of silk, bamboo, eucalyptus and cotton). If my fabric is not real heavy I leave 1/4” extra. I would rather trim a little batting to make it work than wish I had more and try to stuff a little strip in.