Earlier registered users could purge the site cache for a page without confirmation and others were asked for confirmation. Due to T135170 now everyone is asked for confirmation. Recently "without confirmation" part was removed from right's description (T215131), but in Special:ListGroupRights it still doesn't add up quite. It's still listed as right of only the registered users, while actually anyone can purge the site cache for a page.
I suppose this right could be given to all users so that'd it'd better reflect the actual situation. Another option might be removing the right altogether. Comments here suggest that the right might not be needed.