As a social researcher who is also trans, I've found it very difficult to find research (for my literature reviews) that deal with trans experiences because of a problem you've pointed out - sampling is friggen hard. As a researcher, my goal is to at least add trans-specific knowledge to the space.

That being said, at least this report is specific in terms of "this is only LGB" and not misrepresenting it as the entire queer population. In my opinion and experience, it is worth seperating them out in this instance because the trans experience is a lot different to coming out as L/G/B, and comes with its own unique mental health challenges.