Understood, but part of exam prep is completing practice problems with your particular set of references so you become familiar with them and know where to find things quickly. As everyone knows, the morning is all about speed and finding the formula or code section that the problem needs FAST. (I think we all have spent a small fortune on tabs.)
In addition, the codes I used had notes and highlights for things that I might have overlooked. First thing that comes to mind are all of the crazy footnotes in the ASCE-7 Table 12.2-1 as well as the tables in the NDS.
I don't understand. If it's all open book, why not let examinees bring in their own references?