Even with the crappy first version of the WT3 woofer tester, I saw much better plots than that link shows and that tester has stopped working, so I'm not sure I can be sure it wasn't inaccurate the whole time.
If the designer of this device and software is watching, I want him to know that their customer service left a lot to be desired and that charging for an additional download code when the problem was caused by a failed computer is BS.