Let me try to rephrase the problem.
If I select "Create subfolder based on NZB name", but I do not also select "Unrar to a different folder", I get \download_dir\NZB_name.ext, with all files being downloaded and unRARed to the same folder. It does not create any subfolders at all. I do not think this is the correct behavior. I would expect to get \download_dir\NZB_name\NZB_name.ext.
On the other hand, the option "Create subfolder based on archive name" behaves differently. It creates a subfolder whether or not the "Unrar to a different folder" option is selected. I think this is the correct behavior.