Yeah, it's interesting because it's not the usual set-up where the girl is pining after the guy but the guy just wants a fuckbuddy. Sven has actually made moves to ask her on something like a real date in the past, and Faye was the one who told him it should stay casual-only. If he were a different guy, he might have started pining for Faye instead and we'd be feeling sorry for him, but he's not like that. He cut his losses, shrugged, and went "ok, if that's what she wants, I can do that too."
Of course now Faye has to deal with the fact that what she says she wants and what she does want are different things. But it's on her. Still, it's easy to sympathize because she can't help what she feels, and now she's got herself into this weird situation where she thinks Sven wouldn't want a real relationship with her, and he wouldn't ask her for one anyway because she's always said she didn't want it--and she can't make herself ask him, either.
The point where I stop sympathizing though is where she gets all jealous possessive on him, and tells him he can't flirt with or sleep with other women. She wants to be his girlfriend, maybe, but she's always said she wasn't--so why should he have to act like she is, with all the restrictions but none of the pluses?
He HAS renounced his playboy ways for all intents and purposes, since he hasn't slept with anyone else since he and Faye began hooking up.