Mutations can go wild. DNA data tells us it's human. The bone structure is wayy too similar to a humans to be an alien. Chimpanzees are 99% similar in terms of DNA, but look at that skull - large cranium, flat face, and the way the cranium fuses looks human. Having missing pairs of ribs doesn't seem out of the ordinary especially with poly- or oligo- dactyly. I've studied in introductory detail how repeating units of an organism's body form, and it isn't out of the question if enough cells didn't properly polarize.
I'm really hoping that the tests on its metabolism turns out to be messed up so we can call it a mummified aborted fetus and get it over with. The bones seem like they're overly-round, not fleshed out and complex like adult bones are. Maybe the bone density could be explained by a mutation, which seems to be more plausible than it living for 6-8 years? The pediatric specialist analyzed bone density based on normal developmental standards which may not apply here. Anyways, it is a Chilean - they know that much.
The government isn't deciding whether this should remain a secret. The scientists involved are going wtf over explaining what it could possibly be. But at least it's a good day for them - they usually don't mess around super novel things like this.
While it's likely this isn't a fake, let's not conflate the mystery around it with it being a conspiracy theory. This could be the modern-day equivalent of Europeans first discovering platypuses.