The definition of “Gender” in old dictionaries is about “gendered language” like Las Los etc.

Later the word “gender” seems to have changed its defintion, to now be about how a person presents themselves, example as male or female.

Now the words gender and sex are routinely conflated to mean the same thing,

Which is why the word transsexual was dropped in favor of transgender.

My suspicion is that they were using word games to get around reality.

That reality being, that nobody can ever change their sex.

However, it is arguably possible for people can change their presentation (male or female) quite easily,

So by conflating sex/gender, they have deluded themselves into thinking if a man puts on a dress, he magically has a sex change