(OSX): Isn't Screen supposed to override the Command Window?

I thought that when Screen takes over the whole screen, any user input (keystrokes, say)
would NOT make it through to the command window, and that was the whole reason we
needed special functions for storing input like GetChar (which unfortunately doesn't work
for OS X yet).

But just running the DrawSomeTextOSX demo, I see that this isn't the case. A key pressed
at the kbWait will appear in the command window after the demo is finished.

It gets worse: I'm trying to collect an entire string (a word typed in by a participant) using a
kbcheck loop written by Keith Schneider that I've modified to run until the Return key is
hit. I run this loop while Screen is going (I'm just building from the DrawSomeTextOSX
demo). So now, the entire word typed in goes through to the command window, and the
Return stroke tells Matlab to evaluate that word. This is undesirable.

What's going on here? Why is the input getting through? How can I prevent it from doing
so? Thanks very much,
Jason