I'm guessing not too many guys ever saw a crank ground while still in the block. Wouldn't work on today's high revving precision clearance engines, but back in the day my dad and I long before I was in my teens ground many a rod journals on an old tractor engine even some big truck gas engines without doing much more than dropping the pan and puling the head, snatching out the pistons and rods then grinding the journals enough to clean them up to an undersized bearing. usually right in the field with the plow still in the furrow. He and I sat on the side of the road once and he made a rod bearing out of a piece of his belt so we could make it the 100 or so miles home. Got home yanked the head and pan shoved his crank grinder down the cylinder bore ground that 1 journal installed an undersized bearing and ran the old truck for several more years.
I noticed there are several vintage in the block crank grinders for sale on Ebay similar to the one he had.