Couple of things:
1) The testimony of Dad and Dranov did characterize Mike as shaken up; that doesn't mean they are remembering correctly (again 10 years later) or that might wasn't nervous about lying (if in fact he waited 3 months to tell them).
2) He claims he called Dad from the locker room immediately after. That doesn't mean it happened that way. We have never seen phone records to verify that call. Which I find odd.
Do you think Mike, his father and Dranov conspired to make it appear that he was all shaken up when he saw them at the house the night of after calling them from the locker room? Perhaps Freeh was right about a coverup except it was to coverup to protect Mike McQueary, not the football program.