I'm not sure why the videos have you uploading the root site backup zip file each time you build a subdomain. If you look at the backupbuddy plugin page the zip file is stored in public_html/wp-content/uploads/backupbuddy_backups/
You can use file manager to copy this backup zip file and importbuddy.php to your subdomain folder. No reason to upload it each time you build a subdomain.
Just wanted to share.