From wikipedia: False memories can sometimes be shared by multiple people. This is sometimes called the Mandela effect.
So here’s the thing. I see a lot of people mentioning how the last time blizzard delayed an expansion was TBC, however im absolutely convinced that Cata was delayed too, not only me but a couple of other people I’ve spoken to remember the same thing.
DC Universe (another MMO-RPG) announced a delay around the time Cata’s date was announced.
Both being MMO’s and that news being 10 years old I wouldn’t be surprised if you’re just miss remembering the events in the MMO-RPG scene.
That’s what I believe the Mandela effect was. Stories that overlapped and then people incorrectly remembering and/or spreading the incorrect information.