And maybe the answer is, "....it depends". Maybe when you use coolant, the resulting reamed hole will be to dimension, but when using oil, it doesn't cool the material, the material expands due to heat, and when the material gets back to room temperature it has shrunk just slightly. Or maybe, with heat, the reamer itself expands, and cuts a closer dimension. And if its temperature related, what about different materials' rate of expansion vs the reamers'.
Or if its not heat realated, maybe the oil creates some sort of molecular boundary layer that creates a slightly larger hole.
All I know is to,
"...never get involved in a land war in Asia.’
Vizzini The Sicilian