Yes, but that's changing in practice. "Transgender" traditionally includes transsexuals, intersex, crossdressers, genderqueer and drag, but these terms are now becoming more well-defined and those definitions are becoming part of public dialog. IMO, that "umbrella" no longer is particularly useful when we can so easily make distinctions that were once not very well defined or very well known.
And I applaud that. But as members of the "T" part of LGBT continue to define themselves they're not very interested in being under any sort of umbrella. And I don't think that's divisive. There's nothing wrong with defining one's own identity.
Sure, it's confusing that "LGB" became "LGBT" and has morphed into "LGBTQIA" or even "LGBTQQIAA". Times are changing, and we need to change with them or be stagnant.