I'm not sure where that exactly came from. It's was a running joke because we used to play hide and seek with it. Ready to make some soup? WTF! Why is there a porno mag in the microwave? There was a Big Booty one too that I found under my couch when I was cleaning last week. I threw it out because it wasn't Extreme, though.
I wonder if serious (hardcore) collectors of porn magazines (if there are such people) refer to issue numbers in the way that comic book collectors do. "Actually, if you'll refer back to Vol. 1, Number 3 or Hustler's Extreme XXX, you'll see that . . ."
People on reddit talk about their giant porn folders all the time, so there are porn collectors. I'd never heard of print porn collecting, but there are price guides so they must exist.