As another already said, these official rivalries are hardcoded and are really well. In my latest ML in 19 in Rangers-Celtic derby, the CPU made fir first time more than 5 fouls in 10 minutes game and took a straight red card (and it was not for tackling the last attacking player!)
Furthermore the hardcoded rivalries work better than those created by edit mode, cause they used to produce some cut scene pre-game etc. Not sure about this in 20, cause even a fly swinging its wings results in a cutscene!
Currently playing a ML with Fiorentina and had a cut scene before the derby against Juve, when the chairman (or whoever) told my manager that we have to win for all costs. He said, that we are in front of them in the league table but we should increase the gap.
A quick look at the table showed that I was 24 points behind. Oh Konami....