Yep, I was torn on this. At first, I thought it was a completely inappropriate scene. That shows the premeditation on Steph's part. And that sets the game in a very different light — Cuckold dominant, Steph pushing for it.
But then I thought it was the MC's fantasy of what he imagined her to be thinking. And if that is the case, again, it sets up the cuckold dominant scenario but from the point of view of the MC, not Steph.
Both of those scenarios have me asking, "What the fuck, over?" Of course, it could be none of those things. So I don't get my panties into too much of a twist.
What is nerve-wracking here is that Steph does lose control (on the train path). She says and does things with Donny and then she later insists to the MC that she does not want that in her life. But then she keeps Donny's number, wants to invite him back, and mentions him more than once.
Based on every other interaction (outside of sex with Donny and the fact that she seems so eager to have sex with anyone), she seems to be the level-headed one of them. We see her lose her shit if you push too far, too fast, or too much. This would seem to indicate that she will not just go "off script" and fuck random dudes with or without her husband. But she literally does the opposite.
While I would like to think that the script is solid and this will not devolve into a TAC-fuckfest, it is those odd things that happen that make me nervous. Like you, I am happily along for the ride and immediately bought the game on Steam. But I am hoping it does not go in a certain direction.