I have 5.1 speakers, but I don't use 2 speakers (the two behind us, with analogic black jack) on my PC, so I have 3.1 haha! It's maybe for this?Did you check which xml file did you copy to the dolbyaposvc folder?
Most probably you kept the Dolby Atmos xml file; you have to replace the xml file to Dolby Atmos Speaker System.
The most fully featured version is Dolby Atmos Speaker System, and if you play games, Dolby Atmos Speaker System for Gaming.
What difference do you hear between Dolby Digital Plus Home Theater and Dolby Atmos (UWP)?
I can help you modify the xml to suit the audio better to you.
EDIT: What is the different between "TunedV2" and "Untuned"?
Same for "DAPv251-VLLDP" and "DAPv251-VLLDP120"?