Issues hitting framerate requirement with nothing in a scene

I'm on unity 2019.2 and get weird framerate issues with nearly empty scenes also. I tried turning off vsync and I get near perfect performance, even in my test scenes with two million+ polygons. with vsync, i get that same 67.7 fps, and with vsync off i hit my 80 fps target. What's strange is simple motion (like a cube moving at a fixed or deltatime rate) looks perfectly smooth with vsync off, but with it on at 60fps+ it looks awful, it looks like blurry stop motion, an effect i wouldn't assume would be visibile at a poor but still high framerate.

You mention that turning off vSync isn't "possible" in a VR app. I understand conceptually that it would generate lots of skips when you're rendering at one rate and displaying at another. I haven't been able to find out WHY it's a bad idea to disable vsync, if the result is actually perceptively perfect performance?