Not a myth, absolutely true. And I thank Wooo for the information site he gives. Been suggesting this type of training for a very long time.
Basic theory: With rib box size it is not the rib bone that grows, it the cartilage between the ribs that stretches/expands. The exercise is best approached when that cartilage is still in a plastic state of flux, before it matures and hardens. The mean average for most humans is around 24-26 years of age, when maturity sets in.
Old school training: Lots of men, past and present, have average increases in chest size of 2 to 3 inches (usually within 3 to 4 weeks), with a exercise combo of breathing squats and the breathing straight arm pullover. They were taking full advantage of this very heavy style forced deep breathing training. As stated in the article Pullovers, themselves, do aid rib box growth, even in some older men. This combo also has given 10 to 15 lbs muscle gains. The metabolism becomes primed for gains.)
A favorite exercise of mine is the bent arm pullover & press. I consider it a prime upper body mass builder. (Art Jones was motivated to build his exceptional pullover machine, based of the better qualities of the pullover exercise..his Nautilus cam gear made it all that much the better). If wanting to experiment with the affects on increased chest/rib box/lat/triceps/delt size, that I may suggest the P&P. Some fine a BB harder on the wrist and elbows, while a pair of DB's release much on that tension during the movement This will depend on your personal choice, what feels the best. And Yes, you can work into some very heavy weight, after a while. Some of my best results with the pullover & press was when using it with GVT. Good Luck.