Maybe the difference is that in mine and Xyzcf's case is that we already knew there was OW? Telling was, as we were told, what we already knew, made no difference.
I wonder exactly what measures could you ladies take. I told Mr J in his face I knew there was someone else. It made no difference, and, as far as I am concerned, it did not help prepare for the reality of a spouse who lives to be with OW. There is a big difference between the existence of someone else and a spouse leaving to be with that person.
On the other hand, when I was a teen, my uncle told me he had OW. I did not told my aunt. I did not knew if she already knew, in which case I would be bringing up something she knew and may not want to speak about. If she did not knew, since all I was told by my uncle is that there was OW, I did not knew if my aunt and uncle were, or were not, going to work things out. I could see no positive in I, a teenager, breaking the news to my aunt.
Many years later I found out my aunt had knew for years. My uncle's OW has existed since we were children, but as children we had no clue about it.
What I may do with friends I know are cheating is say something to the friend, not their spouse or partner. I never saw any good in telling a spouse/partner.
I am not hauted by the anonymous phone calls (there were two, one after the one telling who OW1 was) nor by had seen, by chance, Mr J with OW1 once. When we both still lived in the capital and OW1 was around we would always tell each other in which part of town/venues we were going to be to avoid unecessary pain, but that once. For some reason, that weekend, we forgot to text each other.
That night, Mr J told me two people had told him they had seen me with someone (of course they had, I was going out to concerts and dancing with a number of friends, but that was it). I asked him if those people knew what happened, he said one knew, the other didn't. My reply was, the one who knows is an idiot, the one who does not knows likes to ruin marriages. That is my view of people who tell a partner/spouse, they are into drama and ruin marriages. Because, 99.9% of the time someone did that, the relationship/marriaged end right away.
Of course this is my life experience and my way of seeing things.
Yes, we get to be mad/angry at whomever we like. But, in a view, a point comes when we need to realize being mad/angry only hurts us more. Anger can be a great driving foward force. Other than that, it tends to cause damage. To ourselves, as well as to others.
Sometimes good things fall apart so better things can fall together. (Marilyn Monroe)