code LGTM, but I got different results when converting sdf -> usd -> sdf

original:

    <light type="directional" name="sun">
      <cast_shadows>true</cast_shadows>
      <pose>0 0 10 0 0 0</pose>
      <diffuse>0.8 0.8 0.8 1</diffuse>
      <specular>0.8 0.8 0.8 1</specular>
      <attenuation>
        <range>1000</range>
        <constant>0.9</constant>
        <linear>0.01</linear>
        <quadratic>0.001</quadratic>
      </attenuation>
      <direction>-0.5 0.1 -0.9</direction>
    </light>

usda

    def DistantLight "sun"
    {
        float inputs:intensity = 100
        float intensity = 100
        float3 xformOp:rotateXYZ = (0, -0, 0)
        double3 xformOp:translate = (0, 0, 10)
        uniform token[] xformOpOrder = ["xformOp:translate", "xformOp:rotateXYZ"]
    }

converted

    <light name='sun' type='directional'>
      <pose>0 0 10 0 -0 0</pose>
      <cast_shadows>true</cast_shadows>
      <intensity>0.01</intensity>
      <direction>0 0 -1</direction>
      <diffuse>1 1 1 1</diffuse>
      <specular>1 1 1 1</specular>
      <attenuation>
        <range>10</range>
        <linear>1</linear>
        <constant>1</constant>
        <quadratic>0</quadratic>
      </attenuation>
      <spot>
        <inner_angle>0</inner_angle>
        <outer_angle>0</outer_angle>
        <falloff>0</falloff>
      </spot>
    </light>

There is some data that is not common between these two formats, I would say that some of the data might be "lost in translation"