This is just a blind guess since I don't own the game, but could it be that the 60 Hz refresh rate only refers to the graphics, but not the gameplay? If I'm right the game would still run at 20 Hz, while the graphics would be drawn at 60 Hz. That would be pretty pointless since the game would just draw the same frame three times, but it might solve some compatibility problems with modern monitors, so who knows.
Nope, the actual output rate is 20 fps. My GSYNC monitor stays at 120Hz (or whatever I set in the video options) in the main menu, but drops to 20Hz once I load a game.
Same thing happens regardless of whether I choose 60Hz or 120Hz, or fullscreen or windowed.
Even Classic mode does the same thing. I get a nice 120Hz main menu then it drops to 20Hz after loading a game
I don't mind if the characters, effects, etc are all 20Hz.. but the mouse at 20Hz is really rough