Cross-sending is called FXP in video and is(was?) used extensively by all broadcasters, TV channels, etc. So much that it's a must-have functionality for any storage system in this domain.
I remember it more from the times when illegal releases were raced to ftp servers to be downloaded by everybody, pre torrent.
Given SFTP is ssh based, it seems like it could support agent forwarding + an FXP-like mechanism to jump from server to Server w/o transferring to the controlling host ...