I didn't get that Dr. S. saw anything Dr. G. did not. The following is from Dr. G.'s autopsy (any typos are mine, I had to type it in from the scanned report):
"Examination of the skull reveals no evidence of antemortem trauma. The inner aspect of the cranial cavity is examined with light and reveals sandy dirt and an attached small incisor which is adhered to the inside of the calvarium with dirt."
http://i2.cdn.turner.com/cnn/2009/images/06/19/caylee.anthony.autopsy.pdf
Dr. G did not identify exactly where in the cranium this "sandy dirt" and attached incisor were. So Dr. S was correct in saying he could make no determination of how the skull was positioned while this substance was deposited. Dr. S. thought it was brain residue, but did not test this assumption (by having the residue tested). Dr. G. didn't test her assumption that it was dirt either, so that one's a draw.
At this point, I
do wish Dr. G. had opened the skull (so as not to have been attacked on the quality of her work). However, I also think that her decision not open the skull was reasonable under the circumstances. (Lay opinion, and MOO.)