That's interesting; I'm pretty sure that both my original bushing, and the one I installed, and the one I got from TRF just a few months ago, all had plain surfaces. Sounds to me like you might have the wrong one. Er, we ARE talking about the bushing in the bottom of the steering box, right?
The shaft should have the clearance built into it, the bushing can be reamed to exact size. No wearing in should be needed. Should be a "close running fit", which ISTR is .001" to .002" total difference between hole size & shaft size (with the shaft smaller obviously).