I have noticed the same, that illegal formation rules do not work this season. In a game one team played with only one player at the sides, in another game one team had 3 players at the left side: both they did not have any possession penalty.

So, the game becomes brilliant: you have a team 5,0 degrees of quality better, you play a legal 4-4-2 and at the end you lose from a team which had 3 players at the left side (and possession only 60-40 for you)