Recently planted chorus flowers that have not grown yet seem to block mobs' pathfinding. For example, if a chorus fruit is directly between a player and a zombie, the zombie will stand at the chorus fruit until the player moves to an angle at which the zombie walks in a different direction. This seems to affect any mob that will chase players e.g. creepers, zombies, zombie pigmen, etc. It also appears to affect baby zombies and baby zombie pigmen. When the plant grows, mobs behind it will resume pathfinding as normal.