It's because Magne's like his mother, and Rex is like his mother. They're very similar people. And Rex can't remember his past reboots, but he's been through being rejected by society for what he is, too.

But it's not just that; Rex still has the knowledge learned from César helping raise him. He knows what a big brother is supposed to do. Memories are stolen but knowledge remains his. Not that he's thought about that at all.

"Kinda surprised by how much it meant to me. I wanna keep making her proud of me. So, yeah. And she feeds me, too!"