However, the most freelancers get short jobs and many clients, as in the original article is specified, so this just simply works.
EDIT: it seems that as currently implemented, even Upwork is bumping in a search the ones with many hours/money earned. So cheating would be a bad decision, since it may drastically affect your visibility on the site
And may be one of the primary reasons for this "feature". I don't blame them, they are a marketplace and should encourage transactions on their platform.