How do you know they are more effective at it? Who is telling you this? Someone who is driving a barbarians-at-the-gates narrative, and stands to profit for it? Someone who spent their life working in a department that is always asking for more money?

All we have to go on is the word of insiders who work for the various ministries, and all of these insiders have their own agenda. They certainly aren't opening up their organizations to outside verification of their claims!

Also, consider the context in which these negotiations take place. When NK negotiates with the US, this is the most important diplomatic conversation they have going. They are obviously going to put a lot of effort into it - as the outcome may be existential to them.

When the US negotiates with NK, it's just one of five dozen plates it is spinning at any one time. Whatever the outcome is, it's not going to be an existential crisis for the US. It's unlikely to be the most important diplomatic conversation it's going to have, and the Department of State, and the CIA will prioritize its resources accordingly.