If you're using dated backup sets, then rclone would in fact continually upload every day because the folder name itself has changed every single time the backup runs, even though only a few files within the folder have changed.
If you're not using dated backup sets, then it should work fine for you as the datestamp on all of the files is correct, and unchanged files are not updated in any way at all.
But feel free to play around with the rsync options if you choose. On my system, the timestamps are not changing