It doesn't surprise me that a lot of grandfathers used a grinder or other 'barbaric' means to sharpen their knives. The most widely available methods back then were limited (basic stones, files, grinders, razor strops). No Lansky, no GATCO, no EdgePro, no Aligner, no sub-micron polishing compounds. No 'instant sharpening solution' to be delivered to your doorstep by the friendly guy in the brown truck. They simply used the tools & methods that were available to them at the time, most of which were probably purchased at the local hardware store.
We have the wonderful, amazing internet. We can read about & learn in a few minutes what earlier generations might never have heard of in a lifetime. We are SO SPOILED nowadays, with all the options we have at our disposal.