Natural position is literally one of the two criteria in the rulebook to judge whether a ball striking the hand is a handball offence.
Apart from goals scored by handballs, the only two criteria are:
- deliberately touches the ball with their hand/arm, for example moving the hand/arm towards the ball
- touches the ball with their hand/arm when it has made their body unnaturally bigger. A player is considered to have made their body unnaturally bigger when the position of their hand/arm is not a consequence of, or justifiable by, the player’s body movement for that specific situation. By having their hand/arm in such a position, the player takes a risk of their hand/arm being hit by the ball and being penalised
If anything, Eriksen's hand is in front of him, and his movement is as natural as Kim's is, so if that's unnatural then we obviously have two players simultaneously turning around to look at the ball both ending up with their hands in unnatural positions (what are the odds of that), and then it gets headed at him from less than a yard with little time to react and no obvious hand movement towards the ball (because how could he react in that time?).
I think the VAR wanted to give the decision, just like he didn't want to watch the Pellistri incident, and obviously showing the incident as a freeze frame as opposed to in real-time is going to tell a different story than showing how fast it all happens when watching it at full speed. I still don't think that Eriksen's body has become so much bigger (and not in an unnatural way either) by the hand position as it's mostly forward, so from the laws of the game I can't see it being such a big error that it warrants a VAR intervention.