If it's not clear what the correct natural value is, then there should be a 'fixme' tag on the area so that every mapper in the area gets a marker in their editor.
Just adding a wrong tag again is not helpful at all. 

Even the questionable 'hazard' tag seems to be fitting according to the OSM Note that was left here a year ago (there is still a hazard in the area if you try to access it). Contacting that user seems to be a good source for further information...