I have seen a "bike shop" just spread a stem open to change to another size - without retaping the bars.
I WAS TOTALLY SHOCKED AND HORRIFIED!
WARNING DO NOT TRY THIS AT HOME ! OR ANY OTHER PLACE OR ANY STEM!
Maybe it is the : " if you do not know better you can get away with it ",theory.
Charlie Petry Jennersville PA USA
NOTE : Not a shop I use. Think it is a shoe store now.