Article says pilot was with “separatist rebels” in the Katanga province of the Congo. It doesn’t say that it was Belgian mercenary army aimed against Congo Prime Minister Patrice Lumumba. On Katanga “rebels” in Wikipedia: The Katangese secession was made with the support of Union Minière du Haut Katanga, a Belgian mining company, and a large contingent of Belgian military advisers. A paramilitary force designated the Katanga Gendarmerie … was initially organised and trained by Belgium.
“Despite being police procedurals, the books are often scathing in their criticism of force (and of the Swedish state itself, which came from the fact that its authors were both Marxists), such as the drive to militarise the police.”