The term has been LGBT basically from the start, hasn't it? Being iffy on new optional extensions is one thing, trying to act like the T is new gets a much less charitable view from me.
According to wikipedia "LGBT" was from 1988 and "LGB" itself was spreading in the "mid to late 80s".
If you have a stronger source I'm open to being convinced, but otherwise I don't find one anecdotal account very convincing. I can't easily get to the cited books to get any more clarity they might have.
https://www.salon.com/2007/10/08/lgbt/