Your readme says:
If mounted:
Proceed with the backup process.
If not mounted:
Display an error message:
"$mountpoint is not mounted", styled in bold, and exit with code 6.
but this isn't in your script, where it only says:
# Check if back up disk is mounted
if mountpoint -q $mountpoint
then
# Clean up previous log(s)...
Should there be an error handling loop that's missing? e.g. rsync elif echo "$mountpoint is not mounted"...