Steps to reproduce:

1. Open attached project
2. Disable VSync in Quality Settings
3. Change graphics API for Mac Standalone to Metal
4. Build ‘DemoWalk’ scene (Assets/VolumetricFog/Demos/Demo1_Walk)
5. Run the built game (Fantastic, 1440 x 900)
6. Take a note of the player FPS
7. Change graphics API for Mac Standalone to OpenGLCore and repeat steps 4-6
8. Compare the FPS count in both builds, notice that Metal build runs slower

My results (with AMD GPU):
Metal: ~61 FPS
GLCore: ~74 FPS