Description:
"ODST has 2 extra skulls; Third Person and Director's Cut.
Third Person should be obvious, but Director's Cut was going to play commentary as mentioned at PAX '09 here:
http://youtu.be/yh_HSoDmtvM"

Again, if you want to doubt his findings go ahead (even though the PAX video proves its legitimate).

Wonder why they cut the 3rd person skull? seems to work fine...