The plane question stated the plane was `over` the park which implies it is not in the park. If the question instead said `through` the park, the answer would differ.
In at least some countries (such as the U.S., and I would speculate practically all countries in the age of commercial flight and private drones, but I don’t know that for a fact) there are laws that define whether flying “over” a public park means in our out, and the park’s bounding volume is defined with a specific altitude ceiling. (It may be different depending on the type of aircraft, e.g., civilian drone vs emergency helicopter vs commercial airliner, etc.)
The author’s trick worked. People are arguing over whether a hypothetical airplane is in the hypothetical park without knowing the altitude or location, rather than pointing at the fact that he question is intentionally under-specified and the right answer depends on important details that were left out.
"the park" includes not only the ground, but also a certain area above the ground - otherwise someone riding a bike through the park wouldn't be in the park (as they are not touching the ground) but their bike would be. That would be absurd.
You see the issue, yah?