If terrain is modified in the awake function before game load, the game freezes. It also freezes if void is created at this time. If this is acceptable behaviour, there should probably be a note in the documentation.
Right now, I'd say everything in the game is "acceptable behavior". :) CW3 is really considered stable and I don't think you'll see any update rolling out very soon.
Define "freeze." I made a map a while back that did this, it took ages to load, but it never caused the game to completely lock up. If it has changed since then, that would probably be considered a bug.
This file does not load for me. In the event that it does not load for you, here is the script of the single unit:
# test.crpl
# Created on: 9/17/2014 3:25:56 PM
# ------------------------------------------
:awake
50 50 10 SetTerrain
Yeah... that causes an exception because the terrain objects are instantiated yet at that point in the load. So in short, don't do that.