Hi @joshuaWhite,
Sorry about the confusion. We’re in the process of reorganizing Cesium Native right now, so some classes got deleted and stuff has been moved around. You’re welcome to delete any references CesiumGltf/ExtensionModelExtFeatureMetadata.h and CesiumGltf/ExtensionMeshPrimitiveExtFeatureMetadata.h, since they no longer exist in Cesium Native.
Let us know if you run into any further compilation errors!