Biography vs. movie plot
"The shorter biography and "in another timeline" is not at all clear to anyone who didn't see the movie"
Yes, I agree with that, but this isn't about the movie, it's about a character in the movie.  If people want to know something specific about the movie, they need to read the movie article.  We don't want to waste the time of the reader with little details (such as the entire paragraph that starts with "When Marty travels back in time to 1955...") instead of giving them what they are here for: Learn about George McFly.