I'm just assuming Nathaniel got off because while he's blowing Asher, he's also listening and/or watching Anita with Micah and Mephisto. So he's just like... getting his voyeurism in while also enjoying getting Asher off. He's the Super Sub, so he might actually just get off on getting his master (Asher is a Switch, right? So he might view Asher as that) off. I don't even know.

Why am I bothering with logic right now?