Not sure if this is a possible clue or not since my video recordings are at 30 fps while the Vive display is at 90, but I recorded a quick flight yesterday in a Davis D1K (it's on YouTube at https://youtube.com/watch?v=CTQO4WmmnM8).
Thing is I almost aborted it because I was getting a fair number of black flashes. I have things tuned right to the edge of what I can run with certain scenery settings and was seeing which planes would fly smooth and which ones wouldn't. The Davis was a bit over the edge.
Anyway, the mirror view out of SteamVR doesn't look to have a single black flash. It's smooth and continuous. Maybe it's always getting a specific frame in the sequence (rendered, warped, warped...) since I have FSX locked at 30 fps so two frames will need to be old ones warped to every rendered frame. I may not even be understanding the process right. But thought it was odd that the video recording at 30 fps showed no black frames while I was getting them in the display.