Folder tree: "+"-icons also for ZIPs?

[Peter2]

A standard folder-tree displays a "+"-Icon to show that there are sub-folders. If I understand it right ...

a) XnView displays a "+" also if there is a ZIP-file in the folder
b) but the click on this "+" does nothing - no function, no message - but the user does not know why and what ...

So ..
a) Is it described correctly?
b) Could it be improved? Usage of another icon and/or better integration of the ZIPs like folders?

Regards

Peter

[xnview]

XnView doesn't support expand for ZIP files, the status (has children) is from windows api that tells me that there is a child

[Peter2]

XnView doesn't support expand for ZIP files...

But mine does ...(Win 7 x64, XnView 2.22 plus all plugins, also ZIP Pack 1.0)
a doubleclick expands to C:\Users\myname\AppData\Local\Temp\ and shows the files

Peter