IMO it is a good idea to get a female-female adapter for a lot of these chinese pieces. Maybe it's just my water amount preference but I find with some of my pieces like the D020-2-W the water goes up the downstem part pretty far, so i like having the extra clearance imo.
i can't speak for other pieces obv since i only have the D0202W and the D022
i can't speak for other pieces obv since i only have the D0202W and the D022