EMSUSD-1719 units prefs during import

When using the overwrite-prefs method to change the units during import,
we need to compare with the Maya UI units, not the internal units.

(By comparison, when using the scaling method, we are scaling to
internal units.)

lib/mayaUsd/fileio/jobs/readJob.cpp

@@ -495,8 +495,13 @@ void UsdMaya_ReadJob::_ConvertUpAxisAndUnits(const UsdStageRefPtr& stage)
 
     // Convert units if required and different between Maya and USD.
     const bool convertUnits = mArgs.unit;
-    conversion.mayaMetersPerUnit
-        = UsdMayaUtil::ConvertMDistanceUnitToUsdGeomLinearUnit(MDistance::internalUnit());
+    // Note: when changing preference, we need to compare to the UI units.
+    //       When adding scaling transforms, we need to compare to internal units.
+    const MDistance::Unit mayaUnits
+        = (mArgs.axisAndUnitMethod == UsdMayaJobImportArgsTokens->overwritePrefs)
+        ? MDistance::uiUnit()
+        : MDistance::internalUnit();
+    conversion.mayaMetersPerUnit = UsdMayaUtil::ConvertMDistanceUnitToUsdGeomLinearUnit(mayaUnits);
     conversion.usdMetersPerUnit = UsdGeomGetStageMetersPerUnit(stage);
     conversion.needUnitsConversion
         = (convertUnits && (conversion.mayaMetersPerUnit != conversion.usdMetersPerUnit));

lib/mayaUsd/utils/utilSerialization.cpp

@@ -371,7 +371,7 @@ void setLayerUpAxisAndUnits(const SdfLayerRefPtr& layer)
         = UsdMayaUtil::ConvertMDistanceUnitToUsdGeomLinearUnit(MDistance::internalUnit());
 
     // Note: code similar to what UsdGeomSetStageUpAxis -> UsdStage::SetMetadata end-up doing,
-    // but without having to have a stage. We basically set metadat on the virtual root object
+    // but without having to have a stage. We basically set metadata on the virtual root object
     // of the layer.
     layer->SetField(
         PXR_NS::SdfPath::AbsoluteRootPath(), PXR_NS::UsdGeomTokens->metersPerUnit, metersPerUnit);