The MLG format is a standard double elimination format. This gives everyone two lives. The Winners bracket (WB) people still have two lives. The LB people only have 1 life. Big tournaments with a lot of people will generally use a double elim format. No one wants to go to MLG play one game and be done. Its just better to have double elim.
What is it?
The extended series says that anytime two players are going to face each other for the 2nd time, the results from the first meeting will be counted towards a BO7.
Red plays Blue and wins 2-1.
Red plays blue again:
BO7 where Red is up 2-1. If the series ends 4-1 or 4-2 then extended series did not affect this game. The outcome would be the same according to standard double elimination tourney. If Red loses the first 3 games 1-2 then extended series saves Red here. The game would be 3-2 Red.
The only time extended series can affect a match is if the underdog wins 2 out of the first 3. Then there are times that you can say "well extended series saved him." It would be true. However if Red wins out of the first 3 games then Red would also win standard double elim tourney.
The finals of a double elim tournament work like this. The person from WB still has his two lives and the person from LB has only one. They should play a BO3. If WB wins, then its over. If LB wins, then they have to play another BO3. Extended series can come into play here but not at first.
MLG says for the finals you play a BO3. If WB wins its done. Tourney over. If LB wins, then it goes to BO7. Here is when extended series starts. It doesn't start before this. Extended series actually hurts the WB person. Its completely backwards for the finals from the rest of the tournament.
If WB is losing 1-2 in the Finals. In a normal double elim tourney, it should reset. WB should have to win 2 games and its done. However, because of extended series he has to win 3 more to win.
If the two players have already played and the finals starts 2-1 or 2-0 then the WB person does get an advantage because of ES. This then falls back to if WB wins the first 2 out of 3 games then he would've won anyway in double elim tourney.
Understand when extended series actually is in play and when it is just the standard double elim tourney rules. MKP did not win because of extended series and he had to win an extra game because of it.