I think the only reason he may genuinely feel euphoria and pleasure from being physically harmed could possibly stem from his past. it's the same with intimacy most victims tend to be hypersexual, often engaging into intimacy even if they're not really feeling pleasure from the experience itself and he seems to be. So i genuinely think from a psychological perspective this is all tied to his past trauma and the way he carries it in the present, in a way he feels it benefits him, even though in reality it doesn't
<3
(not Being sarcastic just really like how you explained it)
