Wow, I didn't know that, thanks for the heads up!
It's more than just USB headset. FFXIV does not handle audio devices being changed at all. So if you normally switch between saw, speakers, HDMI, a headset, or anything else, you'd need to use a virtual audio adapter to pipe the sound to the right device because switching it in Windows won't work if the game's running.
If you plan on using the headset as your -only- source for audio, then you'll have no issues.
That's pretty much the case as I'm not I my wanting one for communication purposes, but also because I'm moving my PC to the room nearest the baby nursery. She doesn't need to here gunfire and explosions going off haha