Which is a myth. Even in the times when Wallonia was an economic powerhouse there were no transfers. Flanders actually still paid more in taxes even though it was economically less strong.

Case in point: a flat tax was levied on ovens. Which meant that a large industrial oven to smelt iron in Charleroi had to pay the same amount as a small over to make bricks in Eeklo.

Also: the vast majority of the money used for infrastructure was used to help the Walloon industry. Even if the investment was in Flanders like for instance the Antwerp port.

Even more: some investment was explicitly withheld from Flemish regions. Limburg is the only region in Europe that was mining cokes without an industry attached to it. All was immediately shipped to Liège or Charleroi