Following the principle that objects with the same functionality in relation to redstone should have only one of their versions in the creative inventory category dedicated to redstone (like Wooden Doors, which only have the Oak variation in this tab), the bug lies in the fact that Copper Bulbs have all their different oxidation variations present in the tab of redstone from the creative inventory. They all work identically in relation to redstone, with the distinctions between them being the light level emitted and oxidation, aspects that are not linked to redstone.