You could try, but I doubt if it would fly. The overall theme is to warrant everything internal to the engine and exclude everything that just bolts to the engine. They also seem to be excluding everything electrical unless it's internal. And they're certainly not going to cover the spark plugs themselves for 5/100,000.
I think my fear here is that in pulling the plugs, someone dropped something in to the engine and then damaged it. Another reason to have a different dealer look at this. At the very minimum, I'd be starting a documentation trail.