welcome to the forum,
should rclone selfupdate and test again.
afiak, the problem with robocopy is that it does not verify file transfers.
where rclone does verify file transfers, and that might take additional time.
fwiw, non-cloud transfers on windows, i never use robocopy or rclone, except in rare cases.
on windows, i use fastcopy, which does verify file transfers.
and check out my howto guide
https://forum.rclone.org/t/how-to-access-smb-samba-with-rclone/42754
does nothing on local/smb, can remove that.