You have established that blocking off 1 tile constitutes trapping, but here stated that holding an arm over the fence to block objects would allow an “avenue of escape.” I’m not quite sure what you mean by this. I have created a series of sketches to help you understand the confusion. Please indicate at which point reaching over the fence goes from legal non-trapping to illegal trapping. Assume each tick mark is two inches.
If all of these are legal, I fail to see any difference between 12 (reaching two feet over the wall) and a wall that blocks off a tile which has already been established as illegal.
If these are all illegal, many robots would be at risk of breaking the rules accidentally.