Yes, I agree with that ILMT and I think that happens a lot, if not always. And I can also see how, when someone is in the midst of all this, it can be harder to see when the words are not mirrored by the man's actions, because love is seen and felt, as well as heard. I think a lot of people lose their ability to see and feel the truth, when they are in the insanity of an affair.
You see, unless the man in this case ever said he intended to leave his wife and family, I can't see for the life of me how he has "let down" our OP, as she thinks he has. If BBS didn't want him to leave for her (and that's a moot point, it seems) then what could he have done in this situation, when BBS phoned him to say that her H was suspicious and that she wanted it to end? What behaviour would have been acceptable?
Bluff that he would leave, so that BBS could feel that it was her making the decision to stay with her family? Histrionics and sobbing?
If mutual love was expressed between the affair partners in this case - and it was genuine - then the OM is just as entitled to feel "let down" by BBS ending the relationship. I expect the sudden realisation that this was regarded by him as a no-strings relationship hit hardest of all, but the clues would have been there all along and really, the person the OP should be most angry with is herself for missing them, understandable though that might be when in the grip of an addictive relationship.
I do think the gender politics of relationships/affairs are hugely relevant and worth questioning. This is simplifying it here, but if there is no societal stigma attached to a man having a sex-only affair, then he has less expectation or compulsion to fall in love.
Whereas there still appears to be a huge stigma to a woman having sex with someone she doesn't love, or have feelings for. So I wonder whether it becomes a self-fulfilling prophesy that women do fall in love, or think they have - and that in itself eases the guilt somewhat, of betraying her H and colluding in the hurt of another woman and child?
When you consider this alongside Tadpoles's observation, which I agree represents another societal belief - that men's affairs aren't necessarily borne out of marital dissatisfaction, but women's are, then I wonder whether there is a degree of post-affair rationalisation going on here too - and a woman's choices to live her life vicariously through her family are belatedly re-written as being married to a man who controls every aspect of her life?
A good acid test of the latter would be some painful honesty about whether the OP's H would have been described by her as this controlling, before the affair started.
There also appears to be an absolute blind-spot on here especially, that women don't start affairs and take the more active role in the affair starting, when the evidence all around us suggests that this is nonsense. In an emancipated society, it is exactly as we should expect and women are perfectly capable of asking for what they want in relationships and don't have to be passive and wait to be wooed and courted.
Women are just as capable of men of wanting a no-strings affair and their marriages don't have to be unhappy for them to do so.
I just wish female posters in this situation were as honest and self-aware as you, ILMT about those issues particularly.
However, I do understand it can take some time to get there and realise all this, which is why I said downthread that I am not unsympathetic to our OP, but far more sympathetic to the deceived partners, especially as both have gone through the agony of suspicions being denied.
The behaviour they were seeing at home must have been really bad, for them to confront like that. 