Yes but I`m wondering why....
X being quiet possibly due to shame?unresolved trauma/issues etc? or simply not feeling that its nessasary to mention too the world?
Maybe they've moved on and it's no longer significant in their lives? In which case it has nothing to do with it being unresolved or to do with shame but simply a non-issue.
Y talking uuh dont know
I've actually met people like this. Happily speaking to you about something totally unrelated and then suddenly, "...that was back about the time when I was raped..." That totally knocks you for a six. I have no idea how to respond to that apart from, "Wow, I'm so sorry to hear that!"
It's incredibly unsettling to just have someone (especially someone you don't know from a bar of soap) blurting that out to you like it was yesterday's news, but that's how some people deal with it as well.
Z had a life changing event and doesnt want other people to be abused so he/she is trying to support anti abuse?
I think that, generally, people who go into activism try to make people aware of their struggle, of the damage it can cause, of what people who go through trauma like that endure and yes, I think that's their own way of coping too: "It happened to me, I want to stop it from happening to someone else." And I think that's a very noble and constructive way of coping.
In the end though, as Shake&Bake said, people deal with things differently and some are more comfortable to share personal details than others are. What's important, I feel, is to just listen and let people express themselves in whatever way they choose and just support them as much as you can, especially from the perspective of someone who has only a very vague idea what they're going through.
In all three of your examples there could be a plethora of reasons why they react the way they do, the only way to know would be to ask that individual person for their own reasons.