It depends what is considered "cultural". Are the only talking about language-related culture, like literature, theatre, songs, and so on? If that is the case, I would understand the results.
However, if we mean culture in the broader sense of mindset, etiquette and values, then Belgium is very close to Germany, in my opinion. I've always seen Belgian people as French-speaking Germans rather than northern French. For example, as a French-speaking Belgian, I am extremely punctual, usually to the minute. Being five minutes late is unacceptable. Completely different from French people.
Even when we look at the government and the economy, Belgium is like a small version of Germany. Both are decentralised federal countries with strong regional identities. Governments often favour coalition with multiple parties, something that is extremely difficult in a country like France (where they have been squabbling with each others since the time of ancient Gaul).
Both Belgium and Germany are more industrialized than France (or Britain or the Netherlands), with particularly strong pharmaceutical/chemical industries and heavy industries. Industry represents 26% of the GDP in Germany, 24% in Belgium, but only 19% in France, and 18% in the Netherlands.
Historically, Belgium was part of the Holy Roman Empire during its 1,000 years of history. Genetically Belgian people have about the same percentage of Germanic DNA as central West Germans from the Rhineland and Hesse. In France, only the northern tip (French Flanders, Hainaut and Artois) that used to be part of the Southern Netherlands is as Germanic.