Well lets face it the magician trick is to use optic ilusions to create the appearance of magic.
Trying to figure how it might have been done is part of the fun.
As long as it provides wonder in that it works. StarVR said with their concept of dual qhd 210°FOV (horizontal) that consumer PCs not strong enough & currently only available to one commercial partner IMAX Theaters. So if what Starbreeze says is true of their 5k panoramic headset the the alternating panel (eye) render makes sense.
Think of RFactor with a triple monitor setup left front right.. The game has to comunicate with the hmd's render. I do recal there is an pvrserver.dll & either in the windows registry or streamvr config file its called.
If i understand the flow
-Game sends to steamvr
-Steamvr reads config & directs game to use pvrserver.dll
-Pvrserver.dll comunicates to game how to send frames.