You are probably correct regarding this child, this incident, but not necessarily.
I've seen boats turn quickly, and/or hit something submerged, throwing out occupants regardless their seating position. In such cases, the boat driver (holding the steer wheel) may be the least likely one to be thrown out, negating the value of his kill switch.
Also, the dangers of outboard props are not limited to just those who accidently fall out. These dangers extend to anyone in the water. Very easy to be sucked into the prop.
Again, mainly just trying to raise awareness @ prop dangers.
But seeing how common household fans are enclosed in a "cage",
wondering to what extent might some type "cage" be practical for an outboard.