I don't worry about the Romex in the walls. I do think about proximity effect.
Like campfires:
Put your feet in one, you'll be in a world of hurt.
Sit right next to one, you can feel the warmth.
20 feet away, what heat?
So, I like the idea of the "last few feet" of cable connecting my amp (close proximity) to be better than the Romex in the wall or the miles of copper going back to the Electric Co.
I want a wall plug that will screw down on the Romex (hate push on connections) and grips the male end of the plug tight. On the ends of the pc, I want good connectors (I don't like Nickel anywhere).
That's all I want and have. I agree with your tech for the most part.