I don't understand these types of articles, when all one has to do is apply the common sense test.
IMO, the arms (shoulders) are the facilitators which activates the larger muscle groups, and arm size has a solid correlation with body weight and size. Its just common practical sense. If you gain good body weight (by using the facilitators), arm size just follows as you get bigger--"overall".
I know one thing for certain, if I stay at 168 to 170 (at present 7.4% BF), and still bust my ass in the gym, my arms not going to get bigger, unless I gain some weight (even if the fat loss/gain ratio cancels out, if you see what I am getting at).
After losing 40+ unwanted lbs: