What I expected to happen was...:
when I set the Max FPS over 60, it would lock to or try and reach that FPS

What actually happened was...:
What happened was it locked at 60 FPS regardless

Steps to Reproduce:
1. Have Minecraft running in windowed mode (Don't think this is the cause, however)
2. Put FPS above 60, even turn down all other graphical settings to minimal
3. Press F3 to see that FPS is locked at 60