Kaladin managed to surgebind before saying any oaths, so a surgebinder hasn't necessarily said any of the Words.
If we take a look at what the KR used to be, they had Ryshadium, access to Plate (even if they chose not to use it), Blades and had said five Oaths. None of our current characters covers all of these.
While I agree a KR should be used only for someone who has said all Five Words, I see no reason for Radiant to not just be short for Knight Radiant. Dalinar uses 'Radiant' too freely if you ask me. Teft on the other hand insisted Kaladin is still a surgebinder even after two Oaths.
However, arguing about definitions doesn't seem productive. But it would be nice if the fandom would settle for something, because until then it can be confusing in discussions. Although I suppose we better wait for Brandon's definitions.