Sites like Writers and French are still in the Beta phase. They were sites that were proposed on Area 51, garnered enough support, and are actively trying to prove themselves to "graduate" into being a full site, on par with Stack Overflow and the dozens of other sites here.
Since these sites start from scratch, it's unfair to require users to have the reputation necessary to do things like edit (2000 rep on SO and graduated sites) and vote to close (3000 rep). Many of these privileges are freely available to most users during the private beta, but after the private beta finishes they are brought up to the intermediate levels you see on the French faq (1000 rep to edit and 500 rep to vote to close).
So, Jack is at least partly correct, but the reputation requirements are not directly varied with traffic level, but instead with the status of the site on the Exchange.