I don't see them as scroll bar replicas; good ones are very narrow but high contrast, to easily offer a compact visual sense of article length -- rather than page length, an important distinction when there are cited sources, recommended articles, and a footer menu. Different functions.

IMO, they should coexist with a well-designed vertical scroll bar.

Unless they were copying it from somewhere else, what were their arguments to implement it? Is it about gamefication of reading an article?