Notice her regret that she says the cake was not worth eating, does not diminish the fact that the sex was with the om was the best ever.
Which is really the crux of the problem. The lens of regret or remorse can certainly get you to the point where you think "NOT worth it", but, at least in my experience, that can be the case simultaneously with "was the best ever". I've done a lot of "not worth it" (in hindsight) things that were incredible at the time, sexual, personal, taking risks, sports. Lots of things, however, I doubt my W is jealous of my skydiving, one of the things I'd put into the "not worth it" category (and, if she wanted to do it together, I'd do it, because while for me it was not worth it, maybe it would be for her).
not believable when the ww tries sell us that the great sex was now bad because she regrets the damage her banging the om did.
problem is how does a ww get us to believe that
the sex was bad, or that the ww did not do things for the om that she has refused to do for her bh?
No, I don't think that's believable either. At least for me, my memories don't work that way. I have a memory of the good experience and a memory of the consequences. They are independent memories, I've done things that felt wonderful at the time but had awful consequences. NOT worth it. But I still remember how amazing they felt and the experience was, I just won't repeat it because the consequences were so severe.
To your last stanza (sorry, I always read your posts as poetry because of formatting); that's a whole different ball of wax. I do think, in some significant amount of cases, sex with the OM wasn't "best ever". There are a lot of things that a man can do wrong in bed, premature ejaculation being high on that list for affairs, but a whole litany of things/requirements and individual knowledge that an OM would need to have to possibly get into "best ever" category. Now, when you bring in the "did it with AP but not BS" well, in some ways, that's "putting your finger on the scale". Doing more with the AP gives him/her an unfair advantage to make sex better. And perhaps that's why we see that behavior sometimes, yes, the AP is small and has ED, but, if I let him go down on me (and not my H) well, then I can still have "best ever" sex..
And, even with that, the danger of the A, the time apart, the illicit nature of the relationship, the sex in public (commonly), the endless buildup and pining, I do think that there are a significant fraction of female AP's who really don't have "great" (or best ever) sex in their affairs. I have trouble believing the same for men, or, myself personally, all the elements of an A, coupled with the typical acts performed in an A, there's so much "finger on the scale" for me that the woman simply needs to show up and not fall asleep for it to hit "great sex" on my scale. And I think that's part of the male/female divide here, imagining myself in that situation, it's hard to see how the sex couldn't be amazing (and lots of men have reported exactly that to me, amazing sex in an A), but, I really don't think it's nearly as universally true for women. But how do you (as a BS) believe it? Even if only some small percentage of APs have this great sex, there is SOME portion who do. But because it's such a non-starter for R, nearly all will lie about it to the BS. So you really have no idea what you're dealing with, was it amazing but a horrible mistake, or was it awful and also a horrible mistake? I do think it matters, if something is "amazing" but has significant negative consequences you are more likely to be drawn to that thing/do it again. If something sucks and has terrible consequences, well.. For me, it seems that it would be much, much easier to not do that thing again.