I have found extra framing in the area of narrow panels, I have never seen the wall framing set narrower for a panel.
worst I saw was a panel change about 2 years ago where the studs in the exterior wall flexed inward when the panel was removed. when we went to put the new panel in, we had to put a 4 by 4 block across the face of it and gently beat it in with a sledgehammer.