Well, technically because grid tool is a library part, as furniture or any another element. It just uses built-in Add-On, that represents this element as separate tool. So Archicad explodes all structural elements including library parts. Label is 2d element - so Archicad shows it how it is - I don't remember, does Archicad explode for example dimensions into lines and text, but seems all annotations elements Archicad just transfer how it is into worksheet.
