Where does this 'hard/soft' notion come from?
To offer my own input...I have noticed two related but arguably distinct central concepts in aikido. On the one hand, muscling or tension, any excess force, is not in the spirit of aikido; the energy is given by the attacker. On the other hand, when nage/tori/shite/whatever needs to move uke, it is done with a relaxed, whole-body feeling. It may feel like you are not exerting yourself at all, but such movement isn't really 'light', it's just relaxed.
So the distinction between subtle redirection and relaxed-but-powerful movement.