This line stood out second time around

Terramar: "I have to choose soon. Every other griff my age already knows where they belong. I'm still not sure." This suggests to me that, however obvious the episode's resolution might be to us, it isn't obvious to the hippogriffs themselves, and that they do expect to have to choose in such a situation. Maybe there's some cultural reason why splitting environments hasn't been a thing up until now, but that's pure speculation.