I think you are correct, which is why the dealer wanted to replace the head. From what I read, it was all the Triton motors, not just the V10, around 1999. I have been lucky that it was only one plug that blew. Probably need to change all of them, but so far, fuel mileage is staying fairly consistent in the 12.5 mpg range, Until something changes, don't think I will risk pulling plugs.
I would change them. If you let the plugs burn wide it is hard on the coils.
The neighbor with his V10 paid $900 to get his plugs changed and they said all 10 broke. (innovation)
It sounds like a genius was working on his truck.