First, this is a very edge case and a very weird example to put into the documentation. I don't know why you'd ever want to do this copy-paste exercise. But anyway, I suspect that you've selected and copied the "wrong" thing. If you single-click directly on the disk you'll see this:

That indicates that you've selected the disk graphic, not the whole output. If instead you double-click away from the disk but in the output cell, you'll see this:

That indicates that you've selected the actual interpretation "value", and copy-pasting that will result in the expected behavior.