When a mob chases a player, that mob normally will try to jump onto one block heights. However this does not happen with azalea despite azalea being somewhat treated as a block.

To reproduce this, place yourself into survival mode. Then, put an azalea between yourself and a zombie. Make sure that the zombie can not get around it. If done properly, the zombie should not jump on the azalea.

Note: This does not apply to all mobs. For instance, I have seen endermen walk on top of azalea, but not zombies or creepers.