Treppy2 hit on the only possible scenario that a tie in game 3 could see both teams advance. That is:
Game 1 low scoring tie; say 0-0
Game 2 the EXACT SAME low scoring tie; 0-0
Game 3 must then be a tie of any value higher than the previous 2 ties. In this example 1-1 would work. And would see the teams in the 1-1 game advance on goals for.
For 2 managers to get together and agree in advance to a tie at a WORLD CUP where a specific number of goals are required seems unlikely.
For 2 managers to agree to such a thing and then actually follow through on it, preposterous.
What manager would see his team score first and then tell his players to let the opponent score? What players would go along with it, when they are in a position to win and advance.
Conversly, what manager would agree to let the other team score first, taking it on faith that they will then be "allowed" to score?
And, it only gets more unlikely as the number of goals required in the 3rd game grows. Say the first 2 games finish 1-1. Then the 3rd game requires a very carefully coordinated 2-2 tie.