It sounds like either I got really lucky with my supportgroup or it's a serious culturedifference? At my group we actually spend more time talking about other stuff then transstuff normally. It's more like a safespace group. And one day you'll have a ton of questions so you talk about it a lot, other days we're talking about tv, sport ...
I agree though, people shouldn't have to disclose being trans. If you want to be out, be out. if you don't, don't. I'm sort of inbetween, being trans is part of my life like having struggled with mental health is. It's something I don't tell everyone and absolutely not as a first thing. But if you've become friends with me you're likely to have heard something about it. But that's also probably because I'm still full on transitioning, it's still this really important thing right now.