In N' Out Flying Dutchman

In N' Out's 'Flying Dutchman' is a grilled cheese sandwich with the bread replaced by meat.  Yeah, I don't get it to be honest, but it's a thing. I mean, I walked up and said "Give me a Flying Dutchman" and the girl knew what I was talking about. I guess this is another in the low carb world, but eat too many of these things and you'll be constipated.