Hi Jason,
That's the behavior of NTM discovery. NTM goes out there and discovers everything related to the data entered into the Discovery Wizard. Filtering is the mechanism we have so you can hide nodes which are least interesting for you to display.
The other option, where you can exclude unwanted nodes being discovered is check the box, Under Discovery settings of your Discovery Scan wizard, which says "Ignore nodes that only respond to ICMP (Ping) If you still aren't satisfied, please share on what we could do better in our future releases.
Thanks Cliton Godinho