Yesterday I had the exact same situation as you. Record 20-2 in RS, PO final, good cup run, large won in last Tv game, but i lost against my rival by 6 points (only 2 balls for that). And the total was 3.5 balls (avarage was above 4).
So I was also assuming that the game against the rival was too important.
After the victory in game 1, today I have similar ratings for the single items, but the total is 4.5 balls. Maybe it was just random then.