To elaborate more on the spoke "spinning freely" I mean that it's not connected to the hub and the nipple isn't connected to the rim. The spoke and nipple are however solidly connected to each other though. Trying to true that spoke would have no effect on the rest of the wheel because it is not connected to the wheel anywhere.

At the hub and rim, the spoke and nipple sit in their places respectively but there is nothing keeping either of them in place other than the drilled holes.