For normal situations that is true. For a variety of non-normal situations you have to use flap 25. One example is whenever Vref is above 167 KIAS (overweight landing) flap 25 must be used to avoid the possibility of flap relief operating. Flap 30 Max KIAS is 180.
Flap 25 still remains approved for a normal landing and is still used by Qantas on some occasions.