I didn't believe their blurb. I've seen some 5¼" disks that are a tight squeeze in most drives, due to the thickness of the mater the jacket was made from. I couldn't imagine compounding the problem by adding a thick label.
I wonder if their adhesive dries out and the holder falls off the floppy... I've always used plain old 33-to-a-sheet address labels. They work in a laser printer and tend to stay on. If you want to remove one, just wipe it with some mineral spirits--it'll come right off, cleanly.