'Trans plus?' I can give you a concrete example.
In Ireland, a group called TENI, Transgender Equality Network Ireland, has a disproportionate amount of influence - when the GRA2015 was being whooshed! through parliament on the coat-tails of the successful Marriage Equality referendum, TENI were deferred to as 'the experts' on the topic by not only politicians, but also medical high-ups. They could present reports or appear at meetings and basically state their demands, and everyone said Oh OK then...
TENI produced a report on transgender students in post-primary education in Ireland, along with the School of Education at the University of Limerick, based on interviews with trans students.
Given that there is only a tiny number of transgender people in the population, the number of transgender students in post-primary education in Ireland must be so small as to make academic research into such a small sample of limited value, other than anecdotal .
And indeed, the impressive-looking report with its methodology and terminology and list of conclusions was based on interview with all of... nineteen young people.
So they managed to find nineteen young trans people in post primary education to interview?
Well no, and this is where the 'trans plus' came in handy - they also included in their study young people who were 'gender diverse' , which they defined as having a 'gender expression different from the cultural norms associated with their birth genders.' This covers a multitude of young people who are not trans, but who reject gender stereotypes - in fact, it could include young gender-critical feminists!
Being 'gender diverse' and being 'transgender' are two very different things, just as LGB are very different from T, but the forced teaming of categories was useful to get up to the number of nineteen subjects.
'Trans plus' can mean anything that's expedient it seems.
The Post-primary School Experiences of Transgender and Gender Diverse Youth in Ireland (2020) Publications – TENI