I'm not interested in sheet metal work. Your question "Is it a bug?" wasted my time. Please include some specific information in your title.
No-no... The Y or K factor compensation. What I normally refer to "stretch and crush" There is that median line through the material that maintains the accurate length through a bend, where, toward the outside of the bend radius, the material stretches... and toward the inside of the bend radius, the material crushes. The two sides of the bends radius have significantly different surface areas.
probably very less time wasted as compared to commenting then again revisiting the same post for replying and may be the third time you will again visit to justify!!
You asked for help, said the answer was inadequate.
I asked for clarification which you have now rudely answered.
What is the answer you are looking for?