The original concept was to attach the forend to the hanger, which also had the mainspring attached.  tying all three parts together could cause accuracy problems. so various fixes were developed----see deHass's books.

Usually the barrel is stout enough its not a problem, except maybe on light whippy barrels.
   Often accuracy tweaking involves anchoring the mainspring hanger solidly to the barrel; or anchoring the forend solidly to the barrel and letting the mainspring and hangar float free.
One commercial barrel tuner for the Ruger SS's uses an externally adjustable pressure point between the hanger and the barrel   (not legal under current ASSRA rules for competition, but helpful for hunting rifles)