They probably are giving a balance point that you would have, if you balanced the plane the "normal" way then removed the wing and checked where the fuselage would balance without the wing.
Doing it this way on some models, makes it easier to insert the battery or weight to balance, without taking the wing on and off every time you try a different position.
I have a carrying handle that bolts in place of the wing on my 63" Sig LT-25, it is marked where the body with the battery should balance. I use several different packs in this plane, so it is easier than having the wing in place.
And in case you think his instructions are strange, look at the way the manual told how to balance the Hobie Hawk.