Yes, I agree with what you say! One point: It does seem to "make sense" that feelings for the OP are usually the result of something missing in the marriage, as you say.
However, a lot of good research on infidelity shows that it also happens in the very best of marriages where neither spouse reports any "unmet needs." And don't forget, "cheating" sometimes DOESN'T happen in marriages where their are TONS of unmet needs! So, I think it's safe to say that feelings for the OP are also because the spouse is just drawn to the specific qualities and characteristics of the OP, just as in "legit" R's. And that is how most straying spouses describe it.
I know for myself, that once my H stopped calling my feelings for OM "silly infatuation" and started acknowledging that the feelings might be less superficial than that, that vastly improved communications between me and H.
