Having served 3 tours on 206, I can certainly confirm that the Sqn was indeed originally No 6 Sqn RNAS - formed during WWI and serving as a fighter Sqn in France. I even travelled with an official party to Armistice Day ceremonies in St Omer a few years back, where we visited the scattered war graves of many Navy (and RAF post April 1918) Squadron members.
Despite the history, we were never referred to latterly as "Naval 6" - perhaps because it just does not have the same ring as "Naval 8".