Merriam-Webster added a definition of the "they" to its Webster's Dictionary. It says "they" also refers to a " person whose gender identity is -binary". These are people who identify as male nor female. Many places use a gender- option on official . Many local governments, schools and have the choice of "X" for people who do not consider as male or female, and for gender people.
Merriam-Webster said using "they" for "he" or "she" recognizes who did not "conform to an expected gender , or who seemed to be neither male nor female". It says the word "they" was used as a pronoun in the 1300s. Shakespeare used in this in the 17th . Also, the 1898 Antony and Cleopatra has the : "No man goes to to be killed....But they do get killed." Many people use the singular "they" .