While not the Congo, events similar to that did happen on lesser scale.

For instance, what became German Southwest Africa started out as a deceptive land purchase by Adolph Luderitz from Captain Josef Frederiks, the area native chief (despite the super German sounding name). Luderitz wrote the contract to specify the measure of land purchased in "geographical miles". Before reading of this in "African Kaiser" by Robert Gaudi, I had never even heard of this metric, so I can pardon Josef Frederiks. Frederiks assumed that he was selling English miles (as we know then in the USA today), but the geographic mile is roughly 4.5 times longer. Luderitz and the other European witness knew, of course, that Frederiks had no idea what was going on.

I doubt Luderitz was the only European to exploit contract semantics to defraud locals out of land with dodgy deals.