Thunar assigns date stamp of deleted file when previous (e.g. original) copy of file copied or moved into that directory

While changing directory structures and trying to reduce the number of duplicate files on an external usb drive - dragging, dropping and deleting files manually with Thunar - I noticed the above (title/one line summary) in the following situation:

(e.g.) I have 2 identical files 'filename.ext' in two folders:
'folder-to-delete/' contains the original file with the original date stamp,
'folder-to-keep/' has the same file but a different (later) date stamp as it was copied previously (with this problem).

If I delete the file 'folder-to-keep/filename.ext' and then copy or move (drag/drop) the file 'folder-to-delete/filename.ext' into 'folder-to-keep/', the file now in 'folder-to-keep/' acquires a new date stamp (matching the deleted file).

However, if I drag or drop the file into an empty folder which has not previously contained a version of it, the original date stamp is retained (as I require/expect).

If I first move (by drag and drop) the unwanted file 'folder-to-keep/filename.ext' elsewhere, and then copy/move 'folder-to-delete/filename.ext' into 'folder-to-keep/', the original date stamp is retained (as I require/expect).

The problem is independent of whether I empty trash after deleting.

So, is this a bug?
I would expect moving or copying a file to some other folder should retain its date of creation and modification.
Overwriting/replacing the unwanted file with the wanted one should retain date stamp of the wanted.
In the scenario above the new date stamp is incorrect, so I expect this is a bug.

$ lsb_release -rd
Description: Ubuntu 13.10
Release: 13.10
$ uname -a
... 3.11.0-13-generic #20-Ubuntu SMP Wed Oct 23 07:38:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
In a Xubuntu session.

(also asked at askubuntu.com)