They're just like that
Sonic knows Nine is not Tails.
Tails is a happy, brainy, not so little fox, he likes beaches and technology, his favorite food are mint candies and he loves to tinker, and to fly with his twin tails. He has a lot of friends that care about him, and a big brother who loves him.
Nine is an angry, brainy, not so little fox, he doesn’t like hugs, he likes to build technology on his lab and he uses his nine tails to protect himself. He doesn’t have any friends, he is alone, the only person he can trust is himself.
Miles is a not so happy, but still brainy, little fox, he loves planes and technology, he has two tails, and he’s been beat up, bullied, and left out through all his short life because of that. He is smart and kind, he hasn’t done anything wrong, he is just a little different.
Sonic knows Nine is not Tails, but Nine is Miles, and Sonic loves Miles.
Hc that Jackson is fascinated by sunsets, the night sky, stars and space because for the first 16 years of his life he was never able to see and experience them.
Holt is similarly in love with sunrises, the day, the sky and brightness because for 16 years of his life he's only lived in the darkness of the night. It's partly why he's so excitable; he's finally able to experience the day and he has lots of friends to spend it with.