Reporting that on my system, Copy Duplicate produces a copy from which any alternate data streams have been removed. Amongst other things, this can remove metadata, which is surely not the intended behaviour.
As far as I can see, Copy Move, Copy As, Copy FlatViewCopy and the various Clipboard commands for copying and moving files don't do this.
Everything is NTFS, including USBs. I've been testing on directories on D: drive, usually within the same directory. For example, within the one directory on D: drive:
The file Test.txt has three attached ADS files.
I select the file and run Copy Duplicate, assigning the new file the name TestCopy.txt
The new file is created in the same directory, and has no attached ADS files.
On the other hand:
I select the same file and run Copy As, assigning the new file the name TestCopy2.txt
The new file is created in the same directory, and has the same three attached ADS files.