From my experience (playing a lot of h2h) it seems there's an algorithm in place to keep things somehow balanced. This might be giving one of the sides a boost (depending on how good/bad is their recent form) or occasionally changing gameplay settings (so for some days it favors a formation over other and/or either strong or quick players etc.). I don't know if that's true or just my idea and if so how this work, but I could find this making sense. And I have felt this "algorithm" effect both for and against me. It is more common for me to have a series of 3-4 or 5 wins then, 4-5 games without win.
The one thing I can tell for sure is that the game never feels "consistent", playing the same way sometimes you score a lot, other not at all, sometimes you get 90% passing accuracy other 60% etc. The truth is that at some points the game gets totally nerve-wracking (e.g. having an opponent score 4 goals on 4 attempts on 96-97 gk and defenders, or a series of games without scoring against low level opponents).