Can someone explain the internal disagreement in the transgender community about the necessity of Gender Reassignment Surgery?

So I've been reading a few articles online from transgender authors with strong opinions on the topic. And it seems like some authors don't view individuals that go through hormone replacement surgery, with no intention of having genital replacement surgery, as true transsexuals. I'm trying to understand this perspective. I'm purely in the questioning phase at the moment but having male genitals while invasive and useless to me aren't really a massive concern. To me it is more about, well, the rest of my body, and how I present myself socially. One of the authors I'm linking below used the term "transgenderist" to describe people with mindsets like my own. And also incessantly used the word "hiding" to describe this perspective. The second author simply doesn't even recognize individuals who have this perspective as "true transsexuals".

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