If I create a client, and next I create his site, the user will not be able to modify settings as "web quota" or example... If this is not a bug, I think that is a need to implement an option "create as user". Most clients don't want to create all setting for his website to work, they want us to create all for them...
This is the intended behaviour to protect sites created by admin form being changed by the client. Most admins dont want that their clients are able to modify the site settings, when they created the site for the client. This function exists. Go to the client list, click on the login as client button and then create the webiste.