Trans people find their bio sex distressing on some level - so let's not have a collective expression for them which insistently defines them by their bio sex.
And again, Kate has been misinformed. A tiny number of the UK's trans community suffer from gender dysphoria (that is the actual condition as defined in the DSM-V of mental health disorders) which brings with it distress at one's biological sex.
The vast majority of men who crossdress who are included under the trans umbrella and who are the leading force within the current trans activist scene DO NOT SUFFER FROM GENDER DYSPHORIA and therefore DO NOT SUFFER FROM DISTRESS AT THEIR BIOLOGICAL SEX
As truscum et al have so beautifully explained here before, someone who suffers this condition finds the idea of using their male sexual organs (can't say penis anymore or can I?) abhorrent. The vast majority of transwomen in the UK however (that is 80 to 95% of them according to GIRES, the trans rights and education campaing group) are straight, full-bodied men who are sexually active using their male appendage for its intended purpose by having penetrative sex with women.
Those individuals do not find their biological sex distressing, they enjoy it very much indeed. Which is why they are:
a) insisting that you do not have to suffer from gender dysphoria to be trans*
and
b) consequently are pushing to demedicalise the whole issue, because being trans is not an illness or a disorder but a completely normal state of being, which needs to be protected in and of itself but which must not depend on having gender dysphoria and especially not on seeking treatment for it.
Some months age, during the time when I woke up to this issue, I made the exact same statement as Kate and was told in no uncertain terms that I was a terrible transphobe and a dinosaur and a TERF and should never ever dare talk to that group of people again because this view of trans people is too offensive* to be endured.