In anyone, gender dysphoria is an incongruence in how your brain is telling you you should be with how you physically are in terms of your sex/gender identity. Generally, most people can tell they have it, but a lot of people go through therapy where they can actually discuss it with a therapist who's trained in how to identify certain abnormalities in the brain. In some cases, they'll do a trial run of continuing to live as their birth sex & see how they do for a certain time. After a diagnosis is made, they'll make a plan of what the person wants to do for transition, which include socially (stuff like changing their name, going by different pronouns, dressing & styling themselves differently, etc), biologically (going on HRT), & physically (getting surgeries, voice training, etc). However, these are different levels of doing this & people feel differently with what they need to feel comfortable in their own bodies, so everyone's transition is different. Hence why we see a lot of transwomen online still having their dicks, though there's also financial difficulties some people have. Sometimes, yes, there are false positives & those people de-transition hopefully with as minimal damage to their bodies as possible.
Indigo is already doing the going by different pronouns & dressing differently & has kept it up for a few years now, which is why I don't think it's wise for people here to call Indigo "she" anymore. The main sticking point for people is Indy not going on HRT, which they said they didn't want to do back when they made the announcement they're trans. And at 1 point, Indy said they wanted to get their tits chopped off, but hasn't done so for unknown reasons we can only guess at. Yes, Indy's been a troll in the past, but I highly doubt that this is a troll, otherwise they'd have gone back to being a woman by now.
And also a note: I'm not entirely comfortable with calling Indy he/him. I'll acknowledge that's how they identify, but without the HRT & surgeries, I only feel comfortable with they/them as the pronouns. And I've explained why I'm acknowledging Indy's gender identity already.