Hey! When I expose a value or string from a node as an IOBox, and then copy that IOBox somewhere else, the type for the IOBox is kept. This not the case for RGBA IOBoxes. In this screenshot both of the right IOBoxes were copied from the exposed ones on the left.
This actually works the same for all IOBoxes, independent of their type: IOBoxes used for output never have a type assigned but always adapt to whats connected upstream, so when disconnected, show nothing. IOBoxes used for input, always have a type assigned (you can see that by the little white dot in their circle) and behave like you expect.