Personally I don' think the Sam route is realistic. It's more realistic than all the incest routes, that's true, but still not very much realistic. It's rare that a milf with quite some life experience would let a horny and immature teenager seduce and fuck her; such cases exist, it's not impossible, but these are rare.
Women usually are looking for emotional support form their potential partner. They also in general prefer men who are tall and do have a physique, which would enable to protect her. Most women won't openly admit it, but still most of them do secretly like atheltic male bodies (not bodybuilder like, but fit with strong arms). Least but not last, most women prefer men with a decent job and income, who can provide for the family.
Sam got nothing out of this top 3 to offer. And no, Sam being a horny teenager desperately wanting to fuck a hot milf like Sophie and therefore bombing her with compliments, doesn't count as emotional support. Sophie also cannot trust a teenager not to brag about his conquest later on. A severe scandal not only destroying her reputation in the whole town but also her family on top will be inevitable and she should have more than enough life experience to realize that. Sam has proven to be immature more than once, not caring about consequences as many teenagers do, but Sophie doesn't seem to care for whatever strange reason. For me this whole Sam plot feels very much forced.
Sophie is more likely to start an affair with the postman before she'd let a teenager fuck her, who is the neighbor's kid and a schoolmate of her son.
EDIT: I don't favor the possible postman route, I just took it as an example, that this route is more likely than the Sam one, when we're talking about realism in this porn vn.