Nautilus silently destroys nanosecond information in timestamp when copying files/directories

View the timestamp of a file, e.g. using ls -l --full-time. If your filesystem supports nanosecond precision timestamps, you will see an entry like:

drwxr-xr-x 1 user user 0 2018-02-21 00:34:03.537833989 +0000 foobar

Copy the file using Nautilus, and view its timestamp. You will see that the timestamp has been silently truncated (rounded down) at microseconds, e.g.:

drwxr-xr-x 1 user user 0 2018-02-21 00:34:03.537833000 +0000 foobar

This doesn't happen if you move a file/folder, or if you create a new folder using the context menu.

Nautilus 3.26.0 on Ubuntu 17.10