I'm always a little surprised when I don't see mentions of FSP [1] in works like this. For a short time, it seemed to be the warez transfer means of choice for those looking to fly under the radar and avoid detection. (So I'm told.) But maybe it wasn't much more than a footnote in the grand scheme of things.
I always thought FXP was a much more common tool, as you could move releases between beefy servers without having to download them first https://en.wikipedia.org/wiki/File_eXchange_Protocol
I'm old enough to remember when IRC DCC fservs were a popular distribution channel.
My impression was that FSP was when you had an account on a Unix server at a University and wanted to slowly move files without attracting attention
When people had their own internet connected machine other protocols were much better choices.