The banana grove shafts are for use with the adjustable, solid-lifter, iron 273 rockers. The one with just a hole are for use with stamped-steel, non-adjustable hydraulic rockers.
That is essentially correct, however, each will work just as well with the other type rocker. The later shafts without the banana grooves have a larger oiling hole, so they probably flow just as much as the banana groove shafts. Typical of a large company to figure out how to save money by eliminating a machining step. No banana grooves probably saved a lot of money, while increasing the oiling hole probably cost nothing extra.