Set GPLinearUnit type parameter default based on input spatial reference (Buffer Example)

Within a .pyt python toolbox I'd like to have a parameter of data type GPLinearUnit get a default value based on an input Feature Class (FC). The standard Buffer (Analysis) tool works as a great example of what I'm trying to imitate:

The closest I've been able to come is to set units in updateParameters based on the FC spatialReference.linearUnitName, but linearUnitName and GPLinearUnit units aren't the same and there are 50+ linear units. Anyone know a better way to do this or a reference/code somewhere I could at least pull the linearUnitName to GPLinearUnit from?

def getParameterInfo(self):
    inFC = arcpy.Parameter(
        displayname = "Input FC",
        name = "inputFC",
        datatype = "DEFeatureClass",
        parameterType = "Required",
        direction = "input")
    units = arcpy.Parameter(
        displayName = "Distance & Units",
        name="Units",
        datatype="GPLinearUnit",
        parameterType="Required",
        direction = "Input")
    params = [inFC, units]
    return params

def updateParameters(self, params):
    if not params[1].altered and params[0].altered:
        spRef=arcpy.Describe(params[0].valueAsText).spatialReference
        if spRef.linearUnitName == "Foot_US":
            params[1].values = "0 Feet"
    return

I should also point out that this code defaults the distance to 0, where as the Buffer tool I'm imitating is able to set units without a distance.