Yes that's right. At the end of 1952 Alfa Romeo withdrew from grand prix racing. This left only Ferrari, outclassed Maseratis, Talbots and Gordinis plus BRM as the only Formula 1 cars available to contest the grands prix. The race organisers were afraid that nobody would come to watch a Ferrari walkover and decided to run their races for Formula 2 cars. And the World Drivers' championship did the same.
You would be correct to say that Dries Van der Lof and Jan Flintermann were the first drivers from the Netherlands to compete in a World Championship race when they took part in the 1952 Dutch Grand Prix.
The confusion comes since the World drivers' Championship was re-titled "The FIA Formula 1 World Drivers' Championship" in 1981 and people apply the title retrospectively to the earlier World Drivers' Championships.