Turn rate slows at low framerate

[Maet]

I'm testing my GTX 1080 TI that has been crashing on me at different settings and I find that when my FPS goes below 60, my turnrate decreases with it. I do not think that's a normal thing to happen in shooters, but it could be a side effect of G-SYNC? The expected behavior is that my turn rate will feel the same regardless of frame rate.

 

[Maet]

Tracking 1x across my mousepad at 80+ framerate, I can do 2x complete rotations. At 30 framerate, I can do 1.5x rotations.