The raised area you refer to is the cylinder stop. It keeps the cylinder from moving rearward when it is out of the frame. ( as in during ejection of the empty brass)
My old S&W 686 doesn't have it, but a newer model I have does
AFAIK, the newer lugs are part of the frame, and non-replaceable.
Cost while retaining function.I wonder if it was function or fashion?
Cost while retaining function.
It is easier and more accurate to machine it as part of the frame than to drill a hole, press in a separate piece and than hand fit that piece to the cylinder