Being polite I'd say GG is a bit "old-school"
It used to be used a lot back in the very early 1980's when I was in transition by people who, to my naive young eyes, were probably more into crossdressing than people who were going "all the way." (yes I was very naive back then and a lot more judgemental as youth often is).
However on slightly more serious note, even back then those of us who were young and transsexual used to wince when people said it, because it was like "ok thanks for reminding me I'm not genuine then pal!"

It is also made slightly more complex by the fact that in subsequent years the existence of complex genetic and hormonal disorders of sexual development is now far more widely understood (I even have one myself) and hence the rather simplistic xx/xy divide is not now supportable as any sort of absolute yardstick.
Terminology changes all the time. People are constantly seeking to redefine groupings and labels. Personally I don't buy into any of it. I have a trans history and a minor intersex condition, I underwent GCS over 30 years ago, but as to the present I prefer not to sail under any label, but simply to be me.