It's not that I put a lot of trust in manufacturers. When you go to engineering school they teach you that stuff. Then when you work in it you practice that stuff.
As to the EC that didn't find the splice and it failed 2 years down the line, EC did his job properly. That's not on him. That's on the factory who made the wire. There is no way for EC to detect that splice or know about it, and even if he did detect it or find out about it, it's not required to be removed. The manufacturer put it there and knew it was there; it's on them. EC should be paid to fix it if it fails. Just like a car dealer is paid to fix defective airbags, etc.
Thanks for the link to how they make wire, interesting. But the cold weld is that the same as a regular insulated crimp on butt splice?
Now the problem I have is if a splice in a nm-b were to cause a fire and resulted in death I have a hard time believing that a fire inspector or attorney in any way would be able to differentiate fault of who made the splice once the insulation is completely burnt off. I guess it would be interesting to see statistics of fires created due to splices like this. I would bet that most would point the finger to the installer rather than the manufacturer. Because most wouldn't think anything like this should be allowed to leave the plant.
This kind of thing shows the intellect between the average skilled installer using common sense and fudge factors versus engineers taught to push things to the limit.