That may have been used in the early days of mojoPortal but it has not been used in quite a while. It was removed because it is not needed and I don't want to maintain un-needed code especially data access code, because if that method remained on SiteSettings then it would have to be implemented and maintained in every data layer we support. So if you need a method like that you should implement it in your own project for whatever database platform you use.
Best,
Joe