Correct. If windows use surround 5.1/7.1 output and you plug in your headphones , you’ll hear only l/r channels and not the center and other channels where are voices and other sounds.
Workaround is setting up stereo in windows output or if your sound card supports via its software , mixing all output surround channels into stereo , then you’ll hear everything.
Eg, my old Audigy4 7.1 can switch internal mixer to headphone stereo output on the fly, 3 mouse clicks . So windows internal input sounds stays constantly at 7.1ch , but are mixed into stereo internally via soundcard chip, that way I don’t need to fiddle with windows sound control every time when I’m using headphones … for late night flights 🙂 … also it gives somewhat more surround feel in headphones stereo because of effects of mixing in surround input.
Cheers