See Modifying the QAT and Ribbon in Microsoft Word.

QAT modifications saved for all documents are stored in a special file. They are visible in all documents/templates.
QAT modifications saved in the normal template are visible in all documents/templates.
QAT modifications saved in other Global Templates are visible in all documents/templates.
QAT modifications saved in a document template are visible in that template and documents attached to that template.

You can have multiple files that hold QAT modifications active at once. I've have at least five global templates that hold QAT modifications related to resources in those templates. I also have other document templates that have QAT modifications related to resources in those templates or tasks done in documents based on those templates.

I can't conceive of a reason that I would store QAT modifications in the normal template. I do not store macros with which I would use a QAT button in the normal template. Storing them in a different global template makes them easily portable.