They probably could have gotten away with “its”. But referring to children in a manner akin to the way we refer to objects or things also sounds vaguely wrong. So there’s that.
How about “The body of a toddler laid to rest with the head on a pillow in a cave in eastern Kenya is thought to be the oldest human burial ever found in Africa.”
There are details that separate good writing from bad. I guarantee that Katie Hunt is as woke as can be, or bows to the CNN style guide, or both.