Dumb spark plug question

[bugmenot2]

I am changing my spark plug on a 300ex, and I noticed the little threaded tip where the boot goes on is missing. I guess that part is called the "terminal nut."
Anyway my question is if that nut is supposed to be there or not.

[JOEX]

I don't think it's supposed to be there...

[esr250r86]

Some spark plug boots have them because the fitting were it goes into is different sizes. But most you take that part that screws on top of the plug off.