The difference between the original vans wheel pant and the so-called pressure recovery wheel pant is that the aft shape on the PC tailors the deceleration of the flow (and increase in static pressure, hence the term recovery) so that it occurs further forward, before the boundary layer thickens up, which will delay separation and reduce the wake, which is the big drag producer. Anything on the airplane that creates a wake, like a bubble canopy, or big gaps or wheels etc are the biggest sources of drag. The shape of the front of the wheel pant is irrelevant for the most part.
Tailoring this recovery requires a certain amount of finesse, so controlled conditions, attached flow etc. One has these conditions to some extent aft of a smooth wheel pant. I doubt they exist aft of a tire with a ridged tread and a wheel with a recessed hub and a brake disk and caliper, not to mention the gap for that fairing and its support structure. I would expect that flow to be very turbulent and any advantage of a pressure recovery design would likely be lost.
But I would expect that fairing, or spat, to have a drag reduction relative to a naked wheel, since it should reduce the wake aft of the wheel.