Never got the restrictions, myself...I mean, from a purely logical standpoint of the amount of work required to achieve the task, having restrictions on in-game romance would mean one extra check. Yeah, not having it might mean extra dialogue being made, but when it comes to the code itself, it'd take more to be exclusionary.
Besides, they did it with the Bath House in Ultima VII Part I...in 1992. You'd think that, after over 20 years, there would be a game that'd do it outside Fable. Then again, this is only to the best of my knowledge, so take that into consideration.