Unthreaded holes for AC fan motor mounting screws?
Today I visited the parts store that I bought this from and they insisted that this was normal.  He suggested that I use a power drill to drive the bolts into the case  (no tapping of holes involved).  

I followed his instructions and it attached easily and solidly. I suspect that the screws are a stronger metal than the holes in the case and the increased friction from displacing the softer case metal prevents the screws from loosening over time.  This must be their solution in place of using loc-tite or lock washers.