If he has won every game so far, at some point the game will like deliberately favour one side to break the streak. I, myself I went through win streaks and non-loss streaks, but many times, it seemed at some point, the game just intervened to break the streak. That streak of his is in fact an indication that things will probably be on your side for this match. You just have to have a decent formation and decent players in relative to the opponents formation and players. About the achievement, he may have already got it before. If he had not, then the game might allow him to get it. Some things just come by themselves in this game with time as if at some point, the game will provide the necessary (chance, draws and so on) for a team to achieve what it did not. Then, it will up to the team to have the necessary (decent players and formation) to do the achievement that season. It is like the game gives you the chance to achieve something you did not, but you have to take it.
Can you post his team details including the squad and the formation? I am curious to know that.