Hi,
UpdraftPlus just calls PHP's FTP functions. What is done in the protocol handling at the lower level isn't something that a PHP application (like UD) has access to. So, you'd need to file this request in the PHP request tracker.
Note, though, that what Filezilla is doing there is compensating for a mis-configured NAT firewall. That's a handy feature, and it saves time. But, if you control the NAT firewall, it's better to just fix it rather than rely on a clever client that works around the broken-ness.
Best wishes,
David