Why isn't being enough of a qualifier to be trans? Or to fall under the trans umbrella?

Dysphoria is common, yes. Just as brown eyes and brown hair would be in a study of ten trans dudes. Does the majority experience simplify or eradicate the minority experience? If we, as a community, begin saying "Well, out of the trans people I know, more experience dysphoria, so really it only counts if you're dysphoric", where exactly are we going to go but in the direction of cis normative thinking patterns ourselves?

Just because there is a minority that does not feel/experiencing dysphoria, does not mean they are lesser than because the majority does feels it.

Let's just make a scenario where we flip it around.

Say dysphoria is uncommon in the trans community. That NOT feeling dysphoric was the one real thing that made your identity solid. Honest. Truthful. How would you feel if someone where to say to you, "Well... you're dysphoric. I am kind of iffy about the way you identity. I don't trust it." Now, does the feel fair? Validating? I am hoping you're saying no because, this going both ways, is simply ridiculous.

You cannot gain experience or claim that you contribute to an inclusion based community if you're willing to write off the experiences of others within the minority community.

I see things like this constantly, and it upsets me greatly. Because how are we meant to grow and learn and change path ways of thinking if we are so easily falling into the traps of the typical binary system? In the cis male/female binary system we have gender roles, expectations, etc. Why on earth, as a minority, are implementing systems of "true trans" and "false trans" on one simple yes or no (dysphoria) answer?

That's not building each other up. That is contributing to systematic trans exclusion within the trans community.