in what context is the "ezrach" different than the rest of bnei yisroel in halacha because the torah uses the word ezrach?
The Gemara's conclusioin is that the phrase "Ezrach" implies men and not women, and when the Torah adds the letter "Heh" so that it says "ha'Ezrach," that comes to include even women.
Generally, when the verse uses the word "Ezrach," it refers to a member of the Jewish people as opposed to a Ger (c.f. Vayikra 19:34 and other places). Someone who is born Jewish is called an "Ezrach," while a Ger -- who was not born a Jew -- is not called an "Ezrach."