ArcGIS Pro allows the deletion of a system field related to editor tracking in a hosted feature layer even when editor tracking is enabled. If a second attempt at deletion is made on a different system field, the deletion fails and returns an error message.
The editor tracking fields on an exported class from a hosted feature layer cannot be deleted. Upon attempting to delete the editor tracking fields as outlined in step 11 Error 160136: The field is required and cannot be deleted is displayed (the first delete).