You are right, but the same can be done over current Upwork; once I trust a freelancer, I can deal outside the Upwork range, using a normal contract.

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