I’ve been hearing it for a long time too (also GLBT). It’s nothing new, even over here in straightland. I just assumed (perhaps incorrectly) that people who are or once were or might be labeled “deviants” by members of mainstream society had a common interest and supported one another in that; i.e., that it’s more about social and political than strictly sexual lines.
It appears, @seano, that you applied the definition “sexual orientation minority” to it and then asked why all four categories of the term don’t fit the definition. I’d say if all four don’t fit and yet they are grouped together, you’re using the wrong definition.