Might the lighter O2 naturally rise away from the organics layer? It may then be able to oxidize metals and meteors sprayed into the upper atmosphere, eventually falling back down with those compounds to fertilize the substrate.
Wind speed is hundreds of km/h. So, "turbulent mixing processes" rule.
There is plenty of un-oxidized material on the ground. Oxygen just needs to be kept off the carbon. And, it needs stirring. Big meteors could do a bit of that.
Earth gets its stirring from tectonics, which Venus lacks.
