Kamma Vipaka is based on cause, condition and effect. This is the Principle of Causality.
If the causes are there, but the required conditions are not present, the effect won’t manifest. Just like a mango seed has the ability to give rise to a mango tree. But it won’t happen if the conditions are not right, like , watering of the seed, availability of sunlight, good soil, etc.
Same is with the kamma Vipaka. An angami brahma may have accumulated many bad kamma in the past. But the condition for their fruition is permanently eradicated.
För example he may have killed many people in the past. But due to such a light body he cannot be killed. And many more.
If one attains Parinibbana, all the kamma bija become ineffective.
What the Buddha said would have been in accordance with the Causality part as mentioned earlier. Untill and unless, the magga phala is attained, one is bound to suffer the consequences as the conditions may come some day.