more possessions is just like more repetitions of an experiement - toss a coin once, who knows....toss a coin 1000 times you should get close to 50% heads
once in stats class I learned about markov chains ... I know this is elementary for some, but I found it enlightening.....where you model events based on repetitions of events with known or estimated probabilities.
a contest that is modelled by a long markov chain will usually lead to the favorites winning most of the time - take tennis as the example, if you take the scoring system of tennis and play until someone wins 3 sets, then if one player has a 55% chance of winning each point that player will win almost all the matches.....because there are so many points
on the other hand, an event with a small number of events can be a lot more random in terms of who wins - think about the old slowdown basketball games before the shot clock......imagine a game with two or three possessions - who knows who will win.....
so, more possessions ....everything else equal....means the favorite should win more.....SUBJECT to stuff like depth and fatigue etc