Machined hole in top of piston. Why???

I have seen large bore pistons, pistons with the diameter of a 55 gallon drum that had a hole drilled and tapped in the center.
Those holes are used to thread an hook into so the piston can be lowered into the cylinder using a chain fall.
Why a small bore piston would have that is beyond me. If the hole is for manufacturing purposes, they must be using some antique equipment/ processes.