If it was done at the factory, the snout was probably ground undersized and the knurling saved the crank from being scrapped.
that would be my guess as well, as knurling raises the diameter xxx amount during the process, then if oversize to print, it can be re-machined to the desired diameter.
during my extensive machinist career, many, many shafts of all sizes for a vast product line were saved using the same process.
incidentally, this process is very simple, using a simple tool that is just touched against the intended surface with a minimal amount of force needed.
many designs of knurling wheels are available for the same tool, thus only changing out the wheels is the only thing needed to get the design and depth of knurl desired. the amount of wheels for the tool can vary from one to as many as 8 [that was the maximum amount of wheels my shop used] or possibly more, depending on the object and type of material being knurled.
