Although, I don't *believe* they apply to this person. I saw him over the holidays and he seems as he ever did, albeit having grown a bit (which I recognize is not dispositive of transitioning, but it adds a few weights to the scale). Also making transitioning less likely is that his parents are super right-wing FOXNews-watching Rush-listening fundamentalist Christians (of the everyone-who-does-not-believe-in-our-narrow-subset-of-protestantism-is-going-to-burn-in-hellfire variety), who I strongly suspect would not support their child in that situation. Sad, but that's how they are -- at least by all available outward indications.
As you allude to, I'm not keen on invading their privacy. I let my curiosity satiate itself upon superficial small talk at family gatherings because I'm not keen on prying. But by now I'm half-way to the conclusion that there isn't anything being hidden, it really was just because they felt like it. Which made me wonder if other people are doing this too.
As far as truancy goes, I don't know precisely, but they did home-schooled some of their older kids through 8th grade, so I would assume they game the system from that angle, if it is necessary (I've got no clue what is necessary there).