Why does Unraid create different subvolumes for different shared folders?

I expect to implement some automation through the cache rules of different shared folders. For example, I want to create a separate shared folder for qBittorrent downloads and set the mover rule to array->cache. This way, the temporary directory for BT downloads will always be stored in the cache, and once the downloads are complete, they will automatically be moved to my desired storage location in another shared folder, which has a mover rule of cache->array. After the download is finished, qBittorrent will automatically move the files to the new shared folder, and then the mover will automatically move the downloaded files to the array. However, since each shared folder now belongs to a different subvolume, the mv operation in qBittorrent can no longer be completed instantly; instead, it will actually perform a cross-volume copy. Is there any way to avoid this issue?"