This has been covered before, but NJS hubs (and equivalent hubs in other drillings) are actually manufactured by a technique called metalspinning. A blank is put in a metalworking lathe and spun rapidly. A relatively dull tool is then pushed against it and causes the metal to flow gradually to form the shape of the hub, much like one would push clay into shape while spinning on a potter's wheel. You typically make a separate blank for each side and then put them together and use spinning to fuse the two halves together. You will occasionally see signs of this fusion joint at the centerline of the hub.

Metalspinning works out the stresses and any flaws in the metal extremely well so the hubs have very low failure rates from cracking. It also allows the hub flanges to be made very thin (i.e., lightweight) without compromising strength. Spinning doesn't compact the metal structure like forging so it doesn't offer the strength of forging, but forging isn't really relevant for hub design -- spinning is actually a better method. Forging works better for products taking strikes (such as hammer faces) or for products facing lever forces (wrenches, crankarms, etc.). And forging works much better when many forging steps are used (the top Sugino crankarms are forged something like 23 times while 75's are only forged about 6-8 times, for example); on hubs, there isn't much opportunity to do to many forging steps. If one uses a stress-relieved billet of aluminum and then mills (CNCs) it you can get the same net performance as with spinning but you have to leave more metal in place so CNC'd hubs tend to be heavier.