create callback on a physics group not firing

[scrubdade]

I think there is a problem with adding callbacks for physics.group.
Whenever I do this

enemyGroup = this.physics.add.group({
        defaultKey: 'enemy',
        maxSize: 5,
        createCallback: function(enemy){
            enemy.setData('health',3);
            console.log(enemy.getData(health));
        },
    });

the callback doesnt trigger but when i change `this.physics.add.group` to `this.add.group` the callback fires. Is this a bug on Phaser 3? if so is there a work around?