Oilite is a self-lubricating material, with oil impregnated into the bushing material. It has been the preferred type of replacement rear generator bushing since the mid-1950's at least. Just getting the oiler wick close to the bushing is sufficient to allow for seepage through the bushing if any extra lube is needed. It's possible the earlier solid bronze bushings might have needed the slot, but I can't remember ever cutting one in a replacement bushing since I started rebuilding generators in the late 1950's.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!