Something similar was also used by C64 cracker groups adding their intros to cracked games. Before the intro ran, user saw a few seconds of random characters on screen - most likely a buffer for a decompression algorithm. In this was case it wasn't done to ease debugging - it's just that the game itself occupied almost all available memory and the only area left that was big enough was the screen buffer. Plus, the resulitng effect itself looked Matrix-like :)