there is ample evidence that two dimensional wings exhibit ground effect characteristics.
Well, of course. Two dimensional wings are always in ground effect, because they have the flow pattern of a three dimensional wing with infinite wingspan. Not co-incidentally, they also generate lift with zero drag. If you want to see what ground effect does on a real wing, looking at two dimensional diagrams isn't helpful.
Those diagrams may be mid-span flow patterns but without an idea of the scale of the wingspan they're not much use. And since they're unrealistically low for aircraft flight, what use are they for indicating ground effect in relation to aircraft?