We hold the parts to 2.000" plus 0.002", minus 0.000" and the fixture holes are 2.000" plus 0.001" minus 0.000" so in theory the fit is either size-for-size or slightly tight.
Because the fixture is not a full circle and is two parts it is slightly flexible, but not much, a part that is 0.002" undersize placed between two parts the correct size will not be held tight enough to avoid rotating under a heavy cut.
An alternate way for a fixture that can accommodate a greater variation in the part OD is to cut the top clamp into separate pieces which each clamp two parts with a central bolt. This allows it to clamp parts with very different diameters, but there is a problem allowing the part OD to vary, when clamped the centers of the parts are not in line.
An open mind is a virtue...so long as all the common sense has not leaked out.