I have discovered that when you apply a new template to another document it adds the new styles but does not remove the styles that exist in that document. I have searched throughout the support documentation trying to find a statement about whether applying a template just overwrites any styles of the same title and I cannot find anything.

So, then if a specific style set is attached it will allow the user to apply the styles needed to make it look like the template for a specific document, but it will also contain the styles it previously did?

It also totally removed the "Normal" style that was originally in the document prior to applying the new styles. If that is gone and there are styles based on normal, what is it basing them on now? There is no newly defined Normal style in the new set of styles, just Normal,SINGLE and Normal Bolded Text.