I was thinking that that couldn’t possibly be right, Joey-Poey, as the 2005 US Grand Prix had only six finishers (due to the Michelin tyre incident), but you could be on to something.
Was it that in all four of those races, every driver who started the race also finished it? The 1961 Dutch Grand Prix had two non-starters, and the aforementioned 2005 US Grand Prix had 14, but every driver that began those races was classified at the end of it.