I think he thinks he’s the dominant bunny, but she shows no sign that she thinks he is. It’s almost like she’s just indifferent the whole thing. She’ll happily clean him and be cleaned by him but I don’t think she wants to be dominant or submissive, she just wants to exist happily haha.There is also a chance that he is just a dominant bunny. It seems that he is just adjusting though, he could also be letting her know that he's in in charge... But it doesn't seem like that's likely I think he's still adjusting and is a bit dominant. Like Zuppa said are you sure that he's neutered?
I guess we’re not completely 100% sure he’s been fixed, but he came from a reliable rescue who said they had both done. Is there any way of checking for sure without booking a vet appointment?