Dang, I knew you were going to ask that one, as I have struggled with it myself. Why is it not defined??? The length of the flange is defined, but not in the sketch. Why??
Now, to my answer - I do not go back and add that dimension on edge flanges. I also have never seen a case where an edge flange went on a walkabout, so my presumption is that they really are, in fact controlled and just don't let us know.
WT