Windows 10 window photo viewer taskbar bug

I have two questions about Windows Photo Viewer on Windows 10:

1. Why does Windows Photo Viewer show a “2” badge on the taskbar?

When I open the same JPG or PNG image multiple times in Windows Photo Viewer, each opening appears as a separate window. For example, if I open the same image 7 times and then close one of the windows, the Windows Photo Viewer taskbar icon shows a badge with the number 2.

As far as I understand, taskbar badge numbers are normally used to indicate unread notifications or other pending items. However, Windows Photo Viewer does not have any notification system. Why does it show a “2” badge in this situation? Is the number actually related to the number of open windows, or is this a bug?

2. Why does an invisible taskbar icon briefly appear when closing Windows Photo Viewer?

When I close an image opened in Windows Photo Viewer, an apparently invisible icon briefly appears on the taskbar. The icon has a highlighted underline, as if the taskbar is indicating that the application is active, but the icon itself is invisible. Then both the Windows Photo Viewer icon and the invisible icon disappear.

What causes this invisible taskbar icon to appear?