why not use rclone
Because icloudpd supports downloading photos from icloud and rclone does not (yet): https://github.com/rclone/rclone/pull/8734
"why not use rclone (?)"
This is the correct - and obvious - response to something like this.
Unfortunately, I believe that rclone has no support for iCloud photos at this time.
Because icloudpd supports downloading photos from icloud and rclone does not (yet): https://github.com/rclone/rclone/pull/8734