Trying to investigate Windows copy problem, I found that file move dialogs can be absolutely different.
Here is an example. Sorry it is in Russian, so I translated some words in red:
You see, that upper dialog contains file size information while lower one does not. Both dialogs were called similarly by mouse dragging of some folders in windows explorer.
Moreover! After some time of working, upper dialog transformed itself into lower's version, i.e. it lost information about file sizes and remaining time and changed it's template accordingly.