I think the main reason to keep the data on the same datastorage is to continue seeding your torrents without duplicating the files.

*arr services are renaming the downloaded file into a library with metadata that are used by your player or service (Kodi/Jellyfin/Plex) therefore if you want that your torrents client continue seeding after the download you need to keep the file like it was: The solution is hardlink and it only works on the same datastorage, because you just copy the links to a file not the data itself (basically)

if your server and datastorage are on the same local network you could simply mount a remote folder on the server hosting the torrent client so it download directly on the other system that has the storage?

That's what I'm doing currently as "temporary" solution (almost a year now...)

Services (sonarr, radarr, Jackett, Jellyfin, transmission/...) on a Raspberry Pi 4

Raid 5 storage on my computer for the TV Shows Raid 1 storage on a NAS for the movies

Both shared via NFS and mounted on the raspberry pi

(yeah it means i have to keep my computer, my Nas and the raspberry pi ON all the time)