You know, it dumbfounds me, why do people bring up what the main games did and how they did it when considering why Reborn doesn't do it? Has anyone considered the problem isn't always how good the Pokemon is but how POPULAR it is? Why choose anything else when you can just pick this other one, Gyarados i believe the problem was it just steamrolls through the gyms, this could also be something that would happen with Battle Bond Greninja but it might also be too much popularity but it could also just be because it wouldn't fit who knows, but really, how the main games did something does not mean it should impact how things will be done in Reborn and i think it should be considered the main games primarily aimed at a younger audience so i'm pretty sure they would want to make sure lots of popular Pokemon are available early while also making sure competitive players can prepare their competitive teams easier.