first sentence of the article you linked says that hijra are transgender women
it's like us calling sliced fried and salted potatoes french fries while the british call them chips; just because india has a specific term for transgender women doesn't make them a third gender
The indian government recognizes Hijra as a 3rd gender, which proves that gender is a social construct. If it wasn't a social construct, India wouldn't have three officially recognized genders
In the United Nations and WHO, about 63 genders are recognized. The fact that people even recognize genders in the first place shows that it's society and individuals that construct the genders, not biology. Saying 'more than 2 genders doesn't exist' is just blatant denial since society already recognizes more than 2 genders.