Streamed Download Policy for smart proxies is supposed not to cache any content but should request the content directly from foreman.
How reproducible:
Install a smart proxy and configure it with dowload policy streamed. Create a File repository by mounting a media to http://abc.foreman.example/pub/installation_media/meaditest, and create the pulp manifest. Make the content available to the proxy by publishing it to the respective lifecycle and sync it to the streamed proxy.
Result: The file storage is added to the streamed proxy, as the storage space increases by the volume of the media.