Why neither dbs nor users are created under my end-user accounts?
If you have two *SQL logical servers available for signup, then the servers for dbs/logins/users creation are chosen by randomize. Imagine wwwuser creates database A and A1 and A2 users and they all go to sql1.mydomain.com. Then even if you prohibit it for signup, the system will still try to create new dbs and db users of wwwuser on sql1.mydomain.com. And as the signup is turned off on it, neither dbs nor users for this db will be created.