So non-FMJ or ball ammo is actually banned by military use under "war crimes", or so I've been told.
Most guys who shot the M855 or Green Tip 5.56 in combat have said they didn't think of it as a great people-killing round, but that it worked well shooting at people inside of vehicles. The claim was that it would often travel through people.
And yes the soft-expansion of a round into flesh is ideal for causing more damage, but even with FMJ 5.56 the ammo is known to 'tumble'when meeting resistance like flesh.
If something moving fast changes direction there is going to be a lot of energy imparted from that. That's considered a feature of the intermediate rounds as far as I know. There is also papers from the switch from 7.62 NATO that deal with the upsides of the switch including more shots carried by each person.
Better accuracy/less recoil.
But also the doctrine that wounded casualties are preferable to kills because soldiers then have to assist them and get them back to the medical facilities where they become more of a cost on the enemy once again through resources used to heal them.
But that's 5.56, and this is .30-06. Oh and the switch from .30-06 to .308/7.62 NATO I BELIEVE was done assuming .308 was more accurate out at longer ranges, and that was preferable to the extra weight/speed.

The idea of a round with that much weight moving that fast, and not exiting is insane to me. The only partial-explanation I've heard(with no evidence of it) is that he was wearing a possible plate/vest, and the bullet ricocheted off of that into his jugular vein. That's a maybe, but I don't know enough to say that's likely or unlikely.
What I do know is that it was weird for that guy close to Charlie's team to say that Charlie's bones were so strong it stopped the bullet that could have injured other people. I think he called Charlie Superman too.
That's a very weird statement.

Every time we have these monumental events in the USA there is an inherent tendency for us to distrust the official story we are given, but then there's almost always conflicting evidence and testimony followed by all sorts of strange anomalies.
For example: Oklahoma City bombing, 9/11(it's like a labyrinth of rabbit-holes inside of spaghetti), and more recently the Vegas Shooting.
We never get the full picture, but often we also don't have someone who is going to trial. If this kid ends up dead that'll be the final thing I need to say they're lying to us, period. Oh and I almost forget about Epstein, funny that.