Matt is asexual and doesn't like having sex, while Foggy loves sex. So when they enter a romantic relationship Matt is reluctantly ready to offer to keep it open so that Foggy can have sex with other people. As it turns out it's a non-issue: Foggy is more than happy to get his orgasm fix via his hand in the shower, and spend the rest of the time cuddling and bantering and spending time with Matt.