I can currently create a feature service in ArcGIS Pro, turn on labels, share it, and users have a similar experience with data symbology/labeling in both ArcGIS Pro and the ArcGIS Enterprise web map viewer. Only ArcGIS Earth is the sore thumb. The geometric content and symbols render, but there are no labels. To bring ArcGIS Earth into harmony with other viewers, it needs to support labels from Esri's own services.