The study explores how unresolved motions in the Benguela upwelling region affect diffusivity estimates and the need for full diffusivity tensors in models. Using a scalar for lateral mixing can be inaccurate due to directional mixing. Analysis of buoys and simulations shows that diffusivity from particle pairs is lower than expected and that removing the mean flow improves estimates. The study shows the importance of full diffusivity tensors for better model mixing and reducing warm biases in models.