Most motherboards have 7.1 output, which is what is being referred to in the specs. That is for connecting up to 7.1 speaker systems (which have disappeared now leaving mainly 5.1). That is not the same as providing 7.1 to headphones.
Save for a couple of headsets (Razer Tiamat for example), most are stereo (1 speaker/driver in each cup) and use an algorithm to provide cues which give the effect of positional surround sound. With USB headsets, this is often built in to the electronics, such as the Arctis 5, for example.
Headsets that have analogue connection (Arctis 3), rely on whatever they are connected to, to provide the positional surround sound cues. In most cases this will be a sound card, as these algorithms are rarely found on motherboards.
Such a sound card would be, Creative Sound blaster Z, which uses SBX prostudio to provide positional sound to headsets or headphones.
Might sound stupid but does pubg benefit ftom 7.1 or use stereo?
To be honest, I'm not sure if PUBG has options for 7.1 output. It's a game I don't play.
Some games don't have options for 5.1/7.1, just stereo.