Really? This is a really common behaviour, not just in Fusion, but in most programs. Once you drag an object to the edge of a window, the program recognises that you want to drag it somewhere beyond the current bounds of the frame, so it scrolls the view to let reach previously obscured locations. Basically all programs do this, whether it's dragging an active object in Fusion, a file in Explorer, selected text in Notepad++, or a highlighted row in Excel. You probably use this technique yourself without thinking about it; it's hard to move things long distances without it.
Not sure how or why you want to scroll the frame editor if you are already dragging an object.