Game does not actually pause when you pause it

What I expected to happen was...:
When I press 'Esc' on my keyboard (hotkey to pause the game), the game should pause and become inactive.

What actually happened was...:
I noticed that "pausing the game" only stops rendering the game yet is still active. (Ex. I paused my game for a few minutes and when I came back and unpasued it, time rendered and passed extremely quickly. Rain also started suddenly, only proving that the game was active.)

Steps to Reproduce:
1. Open up a singleplayer world in Minecraft Snapshot: 13w41a.
2. Look at the sun/moon/stars.
2. Press the hotkey you have set (default is the 'Esc' key) to pause the game.
3. Wait a few minutes and press 'Back to game'.
4. Watch the time move by as if it never stopped.