The following command works fine, without flattening directory of copied artifacts:

copyRemoteArtifacts from: 'jenkins://<redacted>/test-job', includes: 'folder/file.txt,folder/file2.txt'

The remote files are copied as 'folder/file.txt' and 'folder/file2.txt' as expected.

However, if I just copy 1 file as such:

 copyRemoteArtifacts from: 'jenkins://<redacted>/test-job', includes: 'folder/file.txt'

The copied file does not have the directory anymore, and is copied as 'file.txt' instead of 'folder/file.txt'.