Sorry I don't agree with you figures at all a few weeks later during the Battle of Britain between July and September 1940, the figures were 19 squadrons of Supermarine Spitfires (372 aircraft at peak on August 30) and 33 squadrons of Hawker Hurricanes (709 aircraft on August 30) . The average proportion of serviceable aircraft each morning of that battle was 37% of the Spitfires and 67% of Hurricanes .
The figures vary slightly but the official list of squadron types engaged in the Battle of Britain show the same picture (You must be logged on to see external links
My point being that we had twice the number of Hurricanes than Spitfires at that stage of the war and accordingly you would have been more likely to have seen a Hurricane over Dunkirk than a Spitfire. I am not suggesting that there were no Spitfires over Dunkirk but film directors are more interested in fulfilling audience expectations than giving an accurate picture.
It was a snapshot of one hour in the life of three planes, presumably from the same squadron. There were plenty of Spitfires over Dunkirk. How does this give an inaccurate picture?