If I run this command twice to copy a folder..
Copy c:\test\f1 TO c:\test AS f2 WHENEXISTS=replace
..the second copy fails for each file in the folder.
An error occurred copying "Some File": You can't copy a file over itself.
If I change the target so that it no longer points to the parent folder of the source..
Copy c:\test\f1 TO c:\ AS f2 WHENEXISTS=replace
..both copies work as expected.