The average is definitely not a true reflection of the current ability on all courses, in particular when a new course, and tournament conditions are introduced.
I recently played a lot of rounds on the St Andrews front 9, which I seem to be most consistent on, so my average still looks very good having played just 2 rounds on Oakmont so far. First time was a an astonishing 69, and then a 77, which is probably a bit more representative.
What I know is, if I got really lucky, and hit my timing perfect then I could put in a really impressive round. Guess I need to get and play some more, and watch that average leap up, until I hopefully get myself sorted out. lol