In recent years Nikon has announced development of the 200-400TC and Z 200-600 but then they were both released as 180mm on the short end. And now the 70-180mm rather than 70-200. Is it for technical reasons or is Nikon just trying to differentiate themselves from the competition(i.e. Canon 200-400TC and Sony 200-600)? It makes sense on the 70-180 because it allowed a smaller objective lens element. But on the two super tele zooms the reason is less obvious.