Per the FSM, each cam bushing installed in the gearcase must be positioned with the oiling slot at the exact top of the bore (12:00 position). ¹⁾

Bushings are press fitted into the case. A press fit translates to the O.D. of the bushing being the same as the I.D. of the case bore (for practical purposes here).
When a new bushing is pressed into the case bore, it's I.D is compressed and becomes distorted somewhat.
The bushing in the gearcase is then reamed to the correct size and alignment to the cover bushing.