Why not simply send Mick down the left path and show him returning from the right? That directly demonstrates Mick knows a passage from left to right (at least to all observers at the fork. home viewers still worry about video editing).
With your simple proposal, everyone watching is convinced. In the more complicated version, only the person calling left/right knows for sure. As far as everyone else knows, Mick doesn't actually know the secret and the reporter colluded with Mick to pre-arrange a sequence of left/right calls.
What if Mick Ali were going down one of those twisty waterslide tubes, and could say his secret phrase to shunt himself off to a different fork, so he could come out at a different tube exit at the bottom?
Citation needed.
Maybe the paper should have a preface. It might work for entertaining someone who already knows all about zero knowledge proofs, but it doesn't seem to do much to educate those who do not.
And this is why "How to explain zero-knowledge protocols to your children" is probably the worst way to explain zero-knowledge protocols to anyone. Its not explaining what a zero-knowledge proof is or how it works. It's explaining what a simulator is when proving a protocol is zero-knowledge . Oh, and the explanation only works for interactive protocols.