Dwarf hamster really wants to bite me?

I’ve only ever had Syrian hamsters so I’m not sure if there’s much of a difference in how to treat them. For context, he isn’t my hamster, he belongs to my brother’s girlfriend and he lives in my house. I got back from a long holiday recently and only just got to see him.

Whenever I approach the cage (I try to approach slowly and calmly so as to not frighten him) he runs right up to the bars and tries to seemingly get through them to me. I’ve tried putting my hand in his cage (not going after him, just leaving it there for him to approach me) and every time he runs right up to me and immediately starts trying to bite my fingers. He’ll even chase my hand just for a chance to bite me. I’ve tried giving him treats and he ignores them in an attempt to bite me.

I know that I’m a stranger to him, but I figured he’d just be frightened of me and try to avoid me but its the opposite, he seeks me out. I was under the impression hamsters didn’t have the capacity for hatred but he seems to be doing his best to disprove that lol. His cage looks to be a decent size (L 55 x W 47 x H 37.5 cm, unsure if thats too small) and he gets plenty of food, bedding and toys. Could he just be unhappy with his living situation? It‘d make me really sad to know that he’s stressed out or sad and if he was I’d want to try to make sure things improve for him :(