It is my understanding that in India they sell Twinspark engines which do have a second spark plug. The hole is machined on the right side of the cylinder head where the single spark plug engines have an open area between the valve covers.
This idea is a carry over from some of the older iron barrels that in India, were also equipped with a second spark plug.
In my opinion, this second spark plug is totally useless but the people in India think it is a big bonus to have. Maybe, with their poor fuels it helps but I seriously doubt it.
Anyhow, I think this second spark plug has a different number and I wouldn't be surprised to find that it also has a smaller hex size. That would allow a smaller wrench to be used to remove it.
If I'm right, that could be the answer to the OP's question?