You're missing my point. This is a PC game, coded and using numbers. It's not actually playing a game of football.
How else do you think you hit the instant result button, before a game, and get a different result then when you load up the same save, do nothing different, and hit the button again. There HAS to be something generating a seed/randomiser for the game to do different things in the ME when everything else stays static. No match plays the same, for a reason.
We already know the match result is determined when you enter the match engine, its done, you're just watching a fun replay. The ME changes the result when do you things like, sub, or shouts etc, and recalcs the game again.