I just created a new user, logged in with them and created a site. /var/clients/client4 was not created. The site ended up in /var/clients/client0/web9. The symlink /var/www/moo.com pointed at /var/clients/client0/web9.
Then created a site with admin. It was created as /var/clients/client4/web10. Two symlinks correct as before.
This sounds like a continuation of bugtracker bug #236 where it was only fixed for admin.