In F1 there are limited volumes in which to position airfoils, especially at the rear. It would be difficult to fit a single optimal airfoil within the rear rule-mandated box. Instead fitting multiple-element airfoils
is a better compromise in generating the required downforce. Drag in F1 is always secondary to downforce, so the extra drag associated with multi-element airfoils is something for the engine developers to counter with more horsepower.
Looking (with difficulty) at the forks on the bicycle, it seems to me that the two elements aren't particularly closely coupled, so I'd question whether they are performing as described in the linked article. They also appear quite a distance from the spokes to be having an influence on their aerodynamic performance. Could the forks be designed to help cross-wind stability? i.e., avoiding presenting a blockage to a cross wind.
I wonder if better drag reduction could be realized by shaping the spokes as airfoils rather than cylinders - F1 front suspension style.