Recently in doing research I ran across an article that dealt with this issue. Between 2009 ICC and 2012 ICC the wording changed to require headers to be insulated. It seems that the issue comes about in that voids in headers are required to be filled with minimum of R-3 insulation. My first thought was there were no voids but (the light came on). Headers in code are shown as 2 (2x*) the filler, generally OSB is not a required material. It is installed to fill the void. OSB only has a R-.5 whereas the code specifically requires R-3 minimum. This issue should be addressed at plan review.