The "upd" wasn't a patch for the software. It was an invitation for something else to come through the pipe.
Netcat GUI v13exe upd - Standalone Windows GUI for Netcat - New: TLS tunneling (experimental), theme switcher, macro scripting - Fixed: large file transfer crash, UDP display lag - Improved: tabbed sessions, searchable logs, command builder - Requires: Windows 7+ netcat gui v13exe upd
Understanding Netcat GUI v1.3: A Modern Tool for Payload Delivery The "upd" wasn't a patch for the software