Clay----I think youre refering to hose ends and not AN adapters. While having a swivel stem hose end can solve a 'few' issues with wither install or orientation with another angled hose end, you have to understand what makes it swivel to begin with. The stem of the hose end is attached to the hose, via a crimp collar or a reusable collar. The body of the fitting, where the bend and the flare head is, connects to the stem. That is generally via a lock wire pressed into grooves machined into the stem and the body. There is a short, inserted section of the body that fits inside the stem, and is normally sealed by a single o'ring. The body, now sealed by the oring, and secured by the lock pin, is now free to rotate.
While this seemingly is fabulous, especially for those hose assemblies that have 2 angled hose ends that need orientation, there is a trade off. That trade off is the sealing of the body insert to the stem. Its generally great at working pressure due to some expansion. The issue is a very low, or no pressure, you can get some seepage. Fuels in particular, especially IF the internal oring is not necessarily fuel compatible.
In addition to potential seepage, you can get air leaks. The big disadvantage is that over time, the oring looses its pliablity or deteriorates, and the joint gets alot of movement in it. Movement mean lack of sealing, which in the wrong place could be catastrophic.
Here is an excellent example of a live swivel. Stem/body rotates on ball or needle bearings (ball in this pic), sealed by a fluid compatible oring backed up by a teflon seal, similar to what you might see in a hydraulic cylinder. Components are stainless,or titanium, very precision built, and expensive. I guess if we were to have live swivel stems, they would be like this, but you guys would cringe at the costs. Another drawback of 'industrial live swivels' are the bodies are generally large, and heavy.
So---'probably' the best solution is to use solid stem/body hose ends and orient them correctly as the hose will be installed.
Tom