Fan clutch bushing question

Boy, you guys had me going! I thought, damn, I have 2 #2947's on running cars, and this one not on the running Hemi yet. So I checked it, sure enough, it does protrude out a bit. Well, the water pump shaft has a little bit of a recess around it. I put it on by hand, it fits perfectly. So then I checked the shaft on a small block water pump, same thing. I do not see any reason to be modifying the bushing.