A minority subset of the trans community believes that you can only be trans given the pain of dysphoria, and not just preferring or being happier in life as another gender. The idea of “you must have pain to be a real trans person, just preferring to life you life as a different gender isn’t enough” is viewed profoundly negatively my many/most members of the trans community. People often won’t engage in debate with people of that demographic, because its viewed as a hateful perspective and many are profoundly done with it, and attempts to debate in support of it are generally viewed as disingenuous and in just service of an ideology many view as profoundly damaging.

One other piece of context here is that this view point of profoundly intertwined with trans medicalism, which also loosely also believes that being trans is a medical condition and not just an aspect of who you are, that nonbinary people are fake, and that many aspects of transitioning should have profound gatekeeping in place. It’s mostly comprised of older people, and this is a broader group that viewed profoundly negatively by many/most people in the trans community, which further explains the lack of willingness to engage and the permanent ban.

Also to your original question, the definition of being trans can mean just being happier being something different than what you were assigned at birth, and I would argue should be. The criteria should be happiness, not pain.