Gnome/Troll even isn't really the pre cata event.
It's a temporary event that sets up some lore for cataclysm. A pre event is the lead-up to the expansion and is related to the main evil. And generally quite big.
I wonder how this goes for you guys.
Somebody: "Hey I heard the gnomer event is the pre cata event"
You: "Oh really? Instead of checking your information or questioning it, I just blindly believe you and now rage how blizzard can't make anything cool anymore and everything was better before wotlk!"