I suspect you may have found (and tried) this after you made the initial copy? As per the contextual Help (press F1 with Copy/Delete > Folders page open), this does not update the security on existing files ((if Source rights change). It also does not 'add' the security to existing copies on Destination (that were created without it). You would need to delete the Destination copies and run it again with that setting enabled beforehand.
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