Every inspector I have talked to about these things say they are only approved for joining modules in manufactured homes.
Amp has ping ponged back and forth in the way they market them. They were selling them as a general use item in the 90s, then they pulled back and said they were for manufactured homes. Now I see they are back to saying they can be used in general wiring.
I doubt it is a hazard as much as just being a real PITA when they fail. I assume U/L is saying the failure will be contained in the housing. Bear in mind, U/L is not setting a performance standard, only a safety standard.
If it blows open and doesn't start a fire it is OK with them. The end user may expect a little higher standard.
