Point taken and the site I mentioned confirms what you're saying (
http://devcoprize.africamuseum.be./nl/voorstel.htm "Zij kunnen meedingen naar een prijs op basis van een eindverhandeling op het niveau van licentie of post-graduaat (2e of 3e cyclus)"). However, this site also contains the official rules for the competition (
http://devcoprize.africamuseum.be./en/regulati.htm). Translation used there may be wrong of course, but the phrase "minimum of four years of university studies" makes it clear, I feel. To me that suggests a first main degree. VUB site about the Prize is one of several I've found that also use the same solution.