The etymology of the word Gender completely supports the fact it's the same exact thing as sex The idea that there is a separation between Sex and Gender is an invention of feminists from the 1970s. The etymology of the word Gender comes from the Proto-Indo European word "Gene" which means "To beget, To give birth". It was always tied to reproduction even though gender theorists like to pretend only sex refers to reproduction meanwhile gender means something else.
The argument that there is more than two genders rests entirely on the notion that it is not the same thing as sex therefore it is not bound by the Male-Female binary so they can create an endless amount of genders. This argument falls apart very quickly when you read the old dictionary definitions of the word Gender. Take for instance the definition of the word from Dictionarium Anglo-Britannicum (1730). It says this: "Gender of nouns is founded on the difference of two sexes Male and Female, And they are called from the Latins Masculine and Feminine, And few languages have any more genders but these two; but the Greeks and Latins have another Gender, Which the Latins call Neuter, That is as much as to say neither (Masculine or Feminine) as Homo a Man, Is masculine and Mulier a Woman, Is feminine, And Saxum a Stone, Is neuter. "
Once again, The etymology confirms the contrary of what gender theorists would have us believe: Gender is the same thing as sex.
Here's another from Webster's Complete Dictionary of the English Language (1886): "Gender: Sex, Male or female".
Here's another one from the Dictionary of the English Language by Samuel Johnson & John Walker (1828): "Gender: A Kind; a sort; a sex. In grammar, A distinction of nouns in regard to sex"
And just under that definition: "To beget" and also "To copulate; to breed"
Once again, That pesky connection between gender and reproduction that gender theorists try so hard to ignore!
Here's another from the Modern Dictionary of the English Language, MacMillan (1911): "Gender: kind or sex (Male or female)"
I could list off more but the point is that the premise that the two things (sex and gender) are different is simply false. The etymology of the word does not support that, The historical usage of the word does not support that and that is how we have been using the words since at least the days of Greeks and Romans to this very present day as gender is generally understood to be referring to Male or Female.
To assert that that some anomalies somehow upset this rigid rule of biology is simply absurd. To imply that a male who is effeminate somehow means there is something more to gender than merely male and female is laughable. It doesn't even answer the question of why it even is a distinction worth an identity of its own.