Swivel nuts don't swivel/twist

I just noticed over the weekend that my air distributors from KC aren't actually "true barb" 5/16" connecetions but are swivel nuts attached to flare connections on the check valves. (This was a nice find as I'm contemplating switching all my CO2 lines to 3/16 hose)

I removed one of the gas lines off its check valve and noticed that the swivel nut doesn't actaully swivel - I had to turn the entire hose along with the swivel nut to remove it from the valve. Not a huge deal but kind of a hassle since swivel nuts and flare fittings are there to make things easier and more flexible.

My question is: are there some swivel nut connections that are "sealed" and don't actually twist at all? Or is something wrong with it? I know there's the little washer in there to seal against the metal flare end of the check valve. I was thinking maybe the washers just get jammed up in the barb and swivel nut and this keeps it from twisting. This would explain why I've never had an issue with the swivel nuts on the corny QD's, no washer is necessary.
But then I thought maybe some of the swivel nuts have a "permanent washer" inside of them and this causes them to get jammed up.

Anyway, just wondering if anyone has experince with this.
thanks

I use these all the time and the only time they get jammed up is when you push the hose up snug with the nut. There needs to be a gap between the hose & nut so the nut can turn freely.

I attach the hose to the barb by first screwing the nut to a ball lock connector so it does not move and I have the proper amount of barb exposed. I then make sure there is a gap between the nut and hose before I tighten the clamp.