It could be by accident. He has listed T'Chaka and Concept Art Cap (which were both Sideshow Exclusives) before, only to take it down later.
I wasn't aware of that PCZ snafu with T'Chaka and Concept Art Cap. However, there's no "Exclusive" gray box on the Spidey listing at Sideshow (there is on both T'Chaka's and Concept Cap's). I suppose that could be an oversight by Sideshow, so only time will tell.