I don't think the Farm Progress Show in Decatur IL purposely held down the yields. There were thousands of people in the fields with the combines. And Decatur is the heart of the US corn and bean belt.

Corn yields at the show demo grounds appear to be no more than 2/3 of normal (or less) for this area in the heart of the corn belt.  This is an early variety but may be  more typical than we would have thought earlier. 

Take a look at a couple posts on crop talk regarding the FPS.

Jim at Dawn