I'm not sure what your question is. Forms are "created" as designs in Designer. They can then be gathered (if using fragments) and presented/rendered as fillable forms through LiveCycle Forms, or can be rendered into non-changable but displayable on simple PDF devices like an Ipad or phone with LiveCycle Output.
Which path, Forms, or Output, are you taking? The simple answer is that Forms keeps the template XFA with it so that it is still editable.
Unless, of course, you're asking a more subtle question.
Sorry to not be specific enough. Occasionally, my team receives PDF documents from clients and they ask us to clean up the forms, etc. When forms are generated through LiveCycle, the form can only be edited in LiveCycle, not Adobe Pro. Is there a way to save or export the PDF document from LiveCycle so that it is still editable and updatable through Adobe Pro, rather than LiveCycle?
There are two fundamental architectures for forms... XFA and PDF, or what we call Acroforms.
XFA forms can only be editted in LiveCycle Designer. But the good news is that you can edit the fields and the text and page artifacts in LC Designer.
So it's not a matter of how it was generated, but what it was designed in. Once a form has been done in LC Designer (XFA/XDP) it can only be edited with LC Designer. Acroforms can be edited in Acrobat, but your changes are (primarily) limited the form fields and not the page layout.
You can get a bit of a better understanding of XFA forms from the specification. You can also get a more terse and understandable view in some older pages that describe intelligent documents. (note that these pages seem to have a formatting problem at the moment which should be fixed soon, but the text is all readable).
But, simply stated, it's a fork in the road for the two different form architectures.