I think you're asking for a ridiculous level of detail here. Who remembers when they were told by their parent that they were a boy/girl and when they fully "understood" that?
Whilst I agree.
I don’t think asking for that level of detail is always necessarily done for a bad reason.
People are often naturally curious about differing phenomenons. Particularly recent ones. And the “trans phenomenon” (for lack of a better phrase) is starting to become more and more prominent in our societies recently. Or at least more well known
Due to a growing acceptance and practices that are being actively adopted by professionals.
People will be naturally overtly curious about such a thing.
I think the questions that will inevitably pop up in response will be very naturally overly intrusive and perhaps even clumsy.
I can certainly agree with setting boundaries, I think we can should also expect this level of intrusion. Not because the asker is necessarily doing so in order to be mean. But because humans can be very inquisitive and that manifests in some rather awkward ways.
I am bi racial, although since my cultural background was one that is entirely foreign to my country, I was actually asked all sorts of very weird questions by my peers. And yeah it was actually quite intrusive at times, even questions that seemed to be no brainers. But usually it wasn’t done with a bad motivation. Usually
Just that human curiosity (and possibly Aussies being culturally quite blunt and straightforward) the responses manifested in rather “awkward” ways.