I have made over 100 receiving blankets from flannel -- I have found there is no standard for width or shrinkage. I hate the 1-1.5" labels on the selvages -- I don't consider that part of the fabric width (and have you noticed the labels are usually wrapped inside).
I don't count on the width of the flannel until it has been washed -- I have had it shrink as much as 4" -- sometimes in both directions. It has not stopped me from using flannel, just made me buy enough for my project (I do refuse to buy the flannel with the wide labels, however).
What frustrates me is paying LQS prices and getting a lot of shinkage -- I had one LQS piece that shrank 4" both ways, but another piece of the same brand did not shrink at all. Washing and dryer drying has saved me all kinds of problem with the finished quilts -- better to have the uncut fabric shrink than to have the final quilt wonky becayse I failed to wash everything first.