Trophy ranks and exclusive/incubator creatures

So at each level of trophies there are supposed to be dinos that are more common in incubators. Is this a bug that these dinos don’t have a greater chance to be received in the incubators won from battles? Am I just reading it wrong and it doesn’t mean that?

The number of dinos available in the incubators increases as you promote to a higher arena, but the chance of picking any one of them is the same. That means the chance of having a specific dino is decreased.
For example, in arena 1, there are 4 dinos A, B, C and D, the probability of having any one of them is 25%.
In arena 2 which is higher, there are 5 dinos, A to E, the probability of having any one of them becomes 20%.