Even though patrols spawn "rarely" now, they will spawn very strangely in certain cases. In the day they spawn very often since monsters are forced to spawn only in caves while the illagers have few spawning restrictions, boosting their spawn rate. On superflat during the day, over a hundred illagers will spawn (until the hostile mob cap), drastically decreasing slime spawns to only a few slimes. This can create a huge illager army with multiple leaders and sometimes this army can even be created in a default world. As far as I know, a patrol isn't supposed to be a giantic army!