I think you missed my point.
What are the chances that the parents are going to understand all of those terms anyways? Or even care about the extended? I'd bet they'd care less about what you're into and more of what you're doing.
Well what i was saying was exactly that i don't think it's an extended thing. It's not something extra, optional, additional, or anything along those lines, in my view. It directly describes something different, something distinct. On some levels, distinctions might a bit too detailed and small that they can be left unsaid at first and only clarified if extra clarification is needed, and that's reasonable, but i don't think this level is the same level that you're talking about.
When someone says that they're bisexual rather than homosexual, that means they're attracted to more than one gender, and that's quite different from being attracted to just your same gender. This is not a small piece of information unless you're looking at this like there are just two categories, "straight" and "gay", and the rest is just additional clarification, which i think would be an unnecessarily simplistic categorization for someone who knows better and more importantly, evidently an unhelpful one considering the complexity of the reality of the issue.
You've also lumped in issues about gender identification which i think is even more simplistic, because those are two separate issues. If someone says they identify as a male or female or something else, that doesn't say anything about what they're attracted to, it doesn't address their sexual orientation. Every identification of those has it's purpose and context.
You asked what are the chances that the parents are going to understand or care about those terms. People might not care about things they're not properly knowledgeable or aware of, but once they're made aware, the chances of them caring and understanding the importance of those terms increases. "What you're into" and "What you're doing" are related to each other, and i think the first, granting we're intending to address with it basically "What you are", is definitely more important than just what you're currently doing.