Deliberate mistake: Troy and Chad drive into Riley's Auto Salvage and park the truck beside the trailer office (which Riley steps out of), near a tow truck. During "Boys Are Back", just after the shot with the female silhouette and the line "Save the girl," in the next shot Chad and Troy run past the trailer office, but Troy's truck has vanished. No worries, because the truck is back beside the tow truck after the song. (00:56:50)
Deliberate mistake: At graduation, after Troy is handed the diploma, in the overhead shot the graduates on the left and right stand-up from their seats, then turn and walk towards each other. All their seats simply disappear between shots. Obviously done deliberately for the dance sequence, but a mistake nonetheless.
Answer: I think that they are just props. The owner of those jerseys has no relevence to the plot.. They might just be randomly picked names.