[stevenwoo]

yes, HRTF, just typing hastily. If one enables HRTF support for instance, as this quick googleing finds support in an eight year old query on FMOD, http://www.fmod.org/questions/question/forum-29423/ one needs to support/not support/test all the cases, with the HRTF enabled/disabled, user deciding to use headphones/speakers with whatever configuration they have. Maybe one will decide it sounds better with HRTF on with speakers or decide that's not a good idea and not allow it or not even support HRTF. It's up to whomever made the game to determine how to support whatever the user decides to use. So in the general case of games not just VR, one might have a console version and a PC version and may need to support headphones/2 speakers/multiple speaker set ups and enabling/disabling features on demand per configuration. So back to the original query this requires signficantly more QA/testing than supporting just HRTF with VR headphones.