Sorry for another thread on the topic, but I was looking at my local candidates and the only female candidate is for the Green party, and she has retweeted that phrase (with the addition "Transmen are men) a couple of times today.
It seems like doublethink to me, every time I try to unpick the statement I get all messed up in the process.
So, if transwomen are women, why call them transwomen? Surely just by defining them as transwomen you are saying they are different to women? Transwomen can't insist on women using the label cis and then lay claim to the standalone word 'woman'.
So transwomen are women, ciswomen are women. The word woman applies to people of either category, but they are still separate categories within the single word, which we can't describe. We are not the same, but to state 'Transwomen are women' is to insist that we are.
I don't know how anyone who makes this statement can square all of this. It hurts my head just trying to work out what they mean.