I don't think that yin/yang is best represented by the idea of nage wanting to become uke's center. I look at it more like maybe uke is the white, nage is the black, and the line in the middle is just where people touch. When I look at it I see that one side equals the other. A=B. If one is trying to change the other, A does not equal B anymore. In any case, I can't help but believe that there is a way to do it in which A does not try to outsmart, trick, manipulate, overpower, or any other permutation to B. I've heard teacher's say that although there is movement, you don't move the uke's hand wherever it is placed. Somehow there is a way to move everything except the line where A touches B so that this happens.
You might even be able to say that uke and nage are always one, even before they touch each other. It's more likely that we separate ourselves mentally to play these roles when in reality there is no real separation.
I also have a hard time with the representation that if uke comes with a 10, nage responds with a 2. If that were true, maybe the black side would be 1/5 the side of the white side. Maybe it could be translated as if uke moves the contact line forward with a 7, nage moves around that line with a 7.
To me the symbol could represent how things always are, whether we are aware of it or not. Our minds create the ideas of inequities and so we try to learn how to trick the other side. I like my view because if uke and nage are just relating themselves to the line of contact then size, force, power becomes irrelevant. If A always changes it's relation to the contact point between A and B, then it never has to go into B's rhealm, psychology, or space to produce an outcome. It sounds like what most people are describing is going into the other's side to change them, or trying to force the other side into your side to get an outcome. The symbol doesn't seem to represent that to me.
On a side, I think that I've seen times when nage throws uke, and the uke is in more balance the entire time than nage ever was.