Is there any picture of O'Sensei performing Koshi Nage with feet together? I'm more than ready to change my mind if I see the man himself doing it.
This was posted ;
Right column, second down ... feet seem to be closer together although the hakama obscures stuff as usual.
I'm sure having the feet close together during a transitional movement can still allow the feet-apart stance before and after and that cool look with the hand up in the air. "Shazam!"
I'm also sure Ueshiba's legs were strong enough that he didn't need to have his feet together to get the most strength into his stance and avoid injury. He himself said he could lift a LOT of weight when he was younger.