Per se, no. However, there is an old stereotype that all black people look alike to white people. As a result, some people are highly uncomfortable with the idea that they got Nelson Mandela confused with a different black person.
Another oft-used example of the "effect" is the belief that Sinbad was in the movie Kazaam (instead of Shaq), which is another example of the same issue.
So, to be fair, the broader complaint here is that people would rather invent a supernatural phenomenon rather than admit their memory is a little faulty. But some of the defining examples of it happen to be tied to this unfortunate history.
Um .... the Madela Effect is not supernatural.
It's just a specific (and more widespread) version of false memories that get reinforced through social means. Which are prevalent in all sorts of ways- from misremembered movies lines ("Play it again, Sam," or "Luke, I am your father," or "Beam me up, Scotty,") to basic confusion of historical events (people who confuse the announcement regarding Biko with Mandela or people who confuse the later coverage of Challenger with seeing the event) or other weirdnesses (Fruit of the Loom didn't have a cornucopia behind a bunch of fruit as the logo, Looney Tunes, not toons, Monopoly Man doesn't have a monocle).
It's just a name for a wide-spread false memory.