No the thing about the HDMI dummy,
The System need two screens so that PP uses the internal als reference screen, and the output as fullscreen presentattion screen.
In this setup its possible to grab the fullscreen ppt and send it via ndi somewere, but still its possible to see the reference screen on the laptop. Its usefull to see how many slides are left, when happen what etc...
Without the dummyPlug the system wont be able to use this 2 screen setup inside ppt becouse there are no 2 screens and you only would see the fullscreen ppt on the laptop screen infront of you.