Not Necessarily. Sure, that is one use for form builder. but you can also use it the way you are using it to manually create the pages that would be created by the Data Assist wizard, or the Security Assist wizard.
The problem you are running into is that you are assuming that using form builder will create all of the functionality that the wizards do without having to understand what that functionality is.
Form Builder is only one part of the code that the wizards generate. and some of that code that the wizards generate is not native to form builder or any other extension.
We created the Wizards to be used by people that would just like to push a button and have working pages. if you want to get ore in depth and build the pages from scratch, you can do that too, but you need to have an understanding of what you are doing before that will work out for you.