Yes, you need reprojection to be disabled to capture the real framerate between 45 and 90 fps.
In your example, your max 60fps is misleading, because in reality your game run at 90fps (11.1ms frametime) for 30 frames, then the reprojection kicked in and the game keep running at 45fps (22.2 frametime) for another 30 frames.
It probably could handle 70 or 80 fps, but the projection forced it to run at 45 instead.
This is the good solution when you play, but not for capturing your real performances.

I did some test myself earlier in this thread, mostly to evaluate the impact of some options (windowed/fullscreen, mirrored/vrnomirror) thanks to Vive own logging statistics (a little harder to use but I could get each image frametime).

Ultimately, without any possibility to get stable 90fps most of the time, I settled with a setting which will let me stay above 45 fps at all time (reprojection doing the frame cap for me). As I said, I could bear the framerate under 45fps for long.

I probably should retest if anything has changed since then, and especially if supersampling can be a good alternative to in-game AA (because I can't use both with my specs). I already saw SS won't filter the image the same way but I haven't tested if I can crank up some visual settings thanks to it.