Last year I seemed to recall that you could book your room starting on Wednesday. Am I not remembering that correctly? If I am then this year seem quite different. Starting on Wednesday didn't seem to be an option and booking outside of the block is a tremendously more expensive thing ($500+ for Wednesday night).
It's as if GenCon made a deal with the hotel conglomerate to reduce the span of the block knowing that many many people still needed a Wednesday room.