To be honest, it's not that interesting a debate because there's obviously no defined framework of sexual ethics or practice that the dev is employing, or even trying to employ, while crafting the core narrative. There's a cuckold fetish, there's sexual exploration as a couple, there's hotwifing, there's a little bit of swinging, there's plenty of cheating (mostly the husband, sometimes Anne), there's voyeurism, there's Pandora's Box, there's dancing around the perimeter of incest without ever quite crossing Patreon's line (save for one time)...and I could probably come up with a lot more, but I trust the point's been made.
I think the entirety of the original plan (I'm talking pre-revamp here), which pretty clearly seemed to hinge on whether or not the husband remained in nominal control of his wife's actions and bifurcated depending on whether or not she got in the shower with Martin, has gradually been replaced by a "dump all the paint colors into one vat; who cares, as long as it gets Anne laid" free-for-all, in which there's no guiding principle over anyone's behavior, save for the pursuit of orgasms with Yet Another Partner. It's been said many times above: there is absolutely no reason, save for pure masochism or utter lunacy, that the husband should not only push Anne into having sex with his father, but then be able to decide that he's okay with it. Only the most extreme, put-him-in-a-cock-cage-right-now version of a cuckold fetish would even entertain that plot point, and yet there it is. (As I said before, it's easily solved by taking that choice away from the player, and thus the husband.)
I suppose that one could apply a humiliation perspective to what's going on, but not the one so many posters over the years have posited. If the husband's purpose was to debase and humiliate Anne, a lot more of their actions make sense. Except that he's continually characterized as increasingly indifferent to Anne's fun (when he's not aroused), so that can't be it either. I'm suddenly imagining an alternative universe version of this game, in which the husband found out about Anne's wild college years and is playing a very, very, very long game to punish her for it. It'd be a cartoon motivation, as befits his pre-adolescent personality, but at least it would be an actual motivation.
If I had to describe the story to someone, after all that's happened, I'd probably say that the husband wanted an excuse to fuck other women and figured that if he turned his wife into a slut, she'd have no grounds to object. I think having played the game since the beginning, as many of us have, compels a perspective that someone dipping their toe for the first time wouldn't necessarily see. Unless the pregnancy crisis becomes meaningful this time (which it didn't in the original version), the husband never suffers a single consequence for anything he does. Why not? Because Anne's on a plane getting plowed by his dad. Who engineered that possibility? The husband did.
But no, I don't think that's it either. I just think it's incoherent.