Yes, it includes goals in extra time. And it does not "pro rate" the goals per game average by adding the extra minutes (i.e., you could count a 120-minute game as 1.33 games). While it might be interesting to analyze scoring rates that way, I used the standard way of doing it. Just count the goals and games (no matter how long they last).
Final numbers: Overall goals per match: 2.27 Group stage: 2.10 Knockout stage: 2.75 Another way of looking at it: First round of group stage: 1.56 2nd & 3rd rounds of group state: 2.38 Knockout: 2.75 Goals increased as the tournament progressed.
Bizarre tournament. lackluster at the beginning and a lot to be desired in the final, but the rest of the month was pretty good for neutrals.