If you need me to explain then you are a worse ref than Childs

Why put it on report post VR review if there was no elbow?

An deliberate elbow to the head whether with or without the ball is a deliberate elbow to the head in a sport where head protection is currently the priority.

The ref can put something on report if something happens that he or the TJ did not see fully, a possibility that there "might" have been something is not a reason to penalise, hence why something's go on report, If am wrong fine, but I would bet heavily that will come back as no charge, he didn't lift the arm to use the elbow, he didn't try to strike with the elbow. You are permitted to fend with the hand and you can use the forearm as long as it's as a buffer not in a striking motion.
As for headguards, think it's been proven they make very little difference to the extent of head trauma in the game, it's the brain inside the skull moving that causes damage, headguards don't stop that

Head guards aren't the answer hence why boxing have got rid of them.

A fend is typical performed with a straight ish arm that wouldn't typically result in an elbow to the face should it be mis timed.

I get the sense he did try to buffer him away but landed with an elbow. Is that any different to a tackle to the chest that finished around the head-Thats a penalty. Im not sure intent matters, technique is equally as important.

WQ it's an interesting view, players at kids age are taught to carry the gal both hands with ball against the chest and to use the forearms as bumpers, if a tackler comes in low and hits the elbows that's is the tacklers fault. Hand off in the face is not actually illegal, but it's contact with the head, penalty? Tacklers very often push down on the back of a players head when standing up, penalty? Running player with the ball uses his arm to fend a tackler, tackler makes contact with the elbow, penalty? Unless there is intent in most of those it's seen as no penalty. At the level I ref at players using the head as a lever on the ground I penalise.
The tackler hitting the shoulder and riding up hitting the head is a penalty because the RFL have decided it is. Then again why tackle round the shoulders? Hit beneath the ball carrying arm or around the arm, shoulder is poor technique on the tackler

And before you say it, yes the rules should be the same across the sport, how they are applied at different levels can differ. For me every scrum last night was a penalty, loose fwds never bind, at community level I warn em then ping em they soon learn.
Sadly in the top flight dissent is largely ignored! That's why Danny brough got away with so much, at lower levels i for one certainly deal with it early, but like football what kids see at top level on TV helps no one.
One of my fave calls at the scrum is a reminder they need to bind, they don't play for wigan