A thread from a while ago suggests it might be a multi-thread difference thing:
But rclone copy --multi-thread-streams 0 still pulls 1GiB/s for me no problem.
That and settings --multi-thread-streams=12with cache mode writes did not change:
rclone mount --vfs-cache-mode writes --dir-cache-time 5s --no-check-certificate --multi-thread-streams=12 gremy-copyparty-local: /mnt/user/copyparty
Is still at ~600 MiB/s