"it lists the nut as 30.2mm. It seems weird to see this on a Kubota. I have not done the math, but my 1 3/16" socket fits well "
That is a rather unusual call out, but in this case, 30.2 mm converts to 1.1889 (just over 1 3/16ths). Sounds like Kubota bought or used English sized fittings, at least in this application, then converted the English size to millimeters.
Of couse, the call out may be 30 x 2.0 which is a 30 mm Ø and 2 threads per mm (rather a fine thread for the application, though)...so, the use of an English sized nut seems to be the more sensible answer in this case.