Is it the top that bonded??

maybe because he is the one suffering? as he should

Yeah it is. He's the one experiencing the side effects so it's him that's bonded. He loves him, but doesn't really realize that's what it is he's feeling

The last story that did one-sided bonding, they explained it as an issue where the one who is experiencing problems was the one who was bonded with. So his issue is that he didn't bond with his partner when he should have.