This I understand completely. The difference is my Mom really (really) disliked my (alcoholic) Father by the time they divorced so nothing we could tell her would shock her or hurt her.
And we did. Because, besides discussing it amongst ourselves, who else can you tell lol
However, if that hadn't been the case I would have asked up front, ok what do you not want to hear about, the latest phone call of ramblings or whatever.
But I am also a believer in the truth, but get that they were trying to protect you. I think you handled this so well. I hope you are not still feeling hurt, but I do understand.