It could also be that, like my husband, he only wants deep friendships with benefits; not a casual dalliance but someone he is friends with and cares for but he isn't romantically attracted to. It didn't make him immune to NRE and infatuation!
I think Felix might be the same way, or at least he's expressed the desire for the same kind of relationship with Susan. The level of deep in the FWB configuration is debatable, but he's told me he doesn't want to just fuck and then be done with it, but that he'd like to be able to hang out with her as well, and develop at least some kind of a relationship besides just fucking, albeit not a romantic one (although they are friends already, just not close or intimate ones). I think FWB would indeed describe it best, but I've told him that for most people, FWB relationships are always kind of risky, since at least one of the people involved is usually bound to develop romantic feelings anyway, and that results into a lot of drama, tears and heartbreak, if the relationship structure or the people involved won't allow a reconfiguration. This relationship with Susan has plenty of potential for that, because Susan apparently doesn't want to share her romantic partners, but would be able to share her sexual partners.
FWB or a regular sexual partner is still definitely less scary and more understandable to me than a string of casual one night stands and hook-ups. I honestly don't think that a partner who would want the latter would be a suitable partner for me, even if I'd try to frame it as a series of intimate connections. That framing still helps with FWB though.