I don't know. They probably thought that this was a good shot of the horse, which is what they're trying to sell. The little girl is smiling and the boy looks big enough to be able to pull her back up. In fact it looks like his hands are already on her waist. He's smiling too.
But of course having come from a family that let me do unsafe things on horses whenever the chance presented itself I'm a lot less sensitive than some.

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