Why does FPS double when VSync is enabled? (solved)

I had a number of players test this for me after seeing it on my own computer. A user with a better graphics card had the expected results of ~75 fps with VSync off, and ~60 fps with VSync on. Myself and others with perhaps less capable graphics cards go from ~30 fps with VSync off to ~60 fps with VSync on. Using the task manager performance tab just for reference I gathered these stats on my machine:
VSync off: CPU: 20-24%, GPU: 40%, ~30 fps
VSync on: CPU: 38-39%, GPU: 90%, ~60 fps

So... I don't get it?.... of course 60 fps is better than 30... why does my game run 30 fps when I turn VSync off? This is 3D, 2018.3.9, tested on multiple machines.

My first thought was my FPS counter must be bugged, so I turned on Steam's built-in, and it gave the same results.

 

I've since tried forcing targetFrameRate to 300 and still no change.

 

I bound a key to cycle between vsync 0, 1, and 2. 0 and 2 give almost the exact same results 26-30 fps, 1 gives 58-60.

 

the live version of my game is a build from 2018.2.2 and the vsync settings work properly. I run GPU 100% at 70 fps with VSync off, unlike 2018.3.9. Building a project from scratch to reproduce.

project from scratch worked =o=

 

It was Mirror imposing a "server tick rate". Interesting that VSync ON will override targetFrameRate (and confusing)

 

The given example of higher to lower is intuitive, I just wasn't able to guess that it could produce lower to higher. In the end it was my fault for clicking "find all references" on a call to targetFrameRate instead of "find all", when nothing showed up I thought my solution was clean and I'd already looked into the obvious =[ several hours later there it was in plain sight.