All my half couplings were like that too, but I think it os intentional.. They are only made to take threads from one side. Full couplings will have the female threads on both sides.
Yeh i screwed up. Totally thought i specified full coupling but i didn't i ordered a half.. I substituted a brass 1/2 inch full coupling from lowes. Not as sexy but it works. Still red in the cheeks over my screwup,,,
If you have a tap you could run the thread all the way through and make small full couplings, although they would be more like straight thread instead of tapered thread.