"The Mandela Effect" was a literal psychic medium saying that some people lived in a different dimension in their earlier lives, and also the weirdest excuse for people who didn't care about South Africa or Apartheid to explain their lack of knowledge about what happened there after the got the basics in grammar school.
That may be how the term was coined, but that is not the common usage in my experience. Simply Googling 'Mandela Effect' will yield many examples of widespread misconceptions and false memories that you can easily verify with a few peers. Just because one explanation is implausible doesn't mean the effect isn't real. False memories are pretty common.
I've noticed that I can vividly recall experiences in other countries but my memory has altered itself to match the side of the road I'm currently used to driving on, and have confirmed this experience with others.
The Mandela effect is a form of false memory and often involves confabulation. This often happens with people discussing movies and misattributing actors or scenes to contemporary but different films or actors, etc. It also happens with real life events.
