Hexacopter with 5 working motors - no yaw authority?

Yesterday I have tested whether my hexacopter would fly with one motor less. As expected, when one motor is not working from the beginning, it did fly decently. Except for the fact I had no yaw control - even when pushing yaw fully to one side, the copter did not react.

Is this a bug or a ‘feature’?

I am using the pixhawk 4.
The copter should have more than enough power (6s, 18’’ props, 300kv 5008 motors with AUW of 3.2-3.3Kg (hoverthrottle 33%).

It’s all depending on your thrust reserves, and yaw headroom.
And of course if you have symmetrical power and all motors rotated exactly at zenith.
Next release will manage the remaining power much better in your case.