We're perhaps thinking about two different things. Based on your description, it sounded to me you're talking about an arrangement where one person sleeps around as they please and occasionally "teases" the other about being a little, worthless cuck, but both sides still remaining loving and respectful for each other.
"Playful teasing" about person being essentially worthless simply doesn't remain just teasing with no impact on the relationship. Keep it up long enough and it will get under the skin of person who keeps hearing they're worthless, and take a root in the mind of the person who does the "teasing", as well. Maintaining a good, equivalent relationship in such situation becomes increasingly difficult. The implausible/unrealistic aspect i was referring to was apparent expectations such thing will have no effect on relationship dynamic and the pair will remain as loving and respectful for each other as they ever were.
Just chiming in that those things are usually a matter of degrees and compartmentalization. What you are describing is essentially the worst case scenario of taking it to the max (refering to someone as worthless in a general sense) with the person on the giving end having a sadistic streak and imposing it on the person on the receiving end who is not really into it but isn't putting a stop to their partner (could be an introvert person with low self-esteem but that doesn't really have that kind of masochistic kink).
Usually the lighter approaches can be as simple as the person doing the teasing talking to their partner about how they have the hots for another person, or about how other people could give them a better sexual experience in some aspects. As long as those types of comments and attitudes are kept to specific circumstances and plays then both sides can be comfortable with it without it damaging a mutually respectful relationship. You were asking for games that do this lighter approach thing, there is
Indecent Wife Hana, it does a decent amount of building it up without rushing it and exploring the protagonist's thoughts (the one being teased/cucked), him and his wife also keep having normal "healthy" sex thoroughout the story although those scenes are shortened up/omitted later on for story pacing reasons.
The issue with porn games, and EK's games are no different from this, is that usually story progression is tied to escalating the existing fetishes as much as possible. I think the logic is that you need to have something to hook the player into coming back to play the game in a future session, if it feels like it is more of the same and the rest of the game doesn't have the quality to stand in its own merits, the idea is to intensify what the player previously enjoyed and take it to the next level so it doesn't end up feeling like just more of the same. This is usually fine since porn is about exploring all kinds of fantasies, no matter how ridiculous or unfeasible.
The problem is that sometimes this makes it so a specific dynamic a person is enjoying gets rushed onto something they aren't particularly interested on, but that's just an inherent struggle of games aiming for broader appeal. It is better to shoot for all the extremes to cover more ground and hope the people that wanted a more "middle of the road" approach at least appreciate the buildup parts of it. And in the specific case of ORS, I think that a player that wants that could just do the open relationship but only have 1 of the characters sleeping with other people a lot while the other one only stays in the route with their SO. Such a dynamic probably won't hijack the story into being its own "light teasing" route or have unique scenes, but the variable dialogue of the game could address it.
I think this is sort of universal interpretation for Eva's games -- it's similar in Good Girl Gone Bad, where "open relationship" was effectively the MC and her partner having sex with some third party together, and sleeping with someone behind the partner's back would activate cheating route(s).
To be fair, that's kinda how it works with Eric at the start of GGGB, but the "open relationship" at the end of the game would allow the MC to sleep with other people without it being considered cheating (although I think the wording for it there was a "liberal relationship"? Maybe it is just a Eva Kiss wording kink or something), just a shame that arrangement required a bimbo Ashley and it was portrayed essentially as "MC is just too much of a sex demon to be with 1 person even if she really loves them now and so she seduces and manipulates their partner into agreeing to it" rather than a mutual thing.