Borisvian, whatever is your definition of
leaning with torso and whatever is your position in the space, if you can stay balanced alone it necessarly means that you are
not sharing weight at all.
This is a basic mechanical concept: if your center of mass is above the area between your feet, then you can stay balanced alone, otherwise you need someone else to support part of your weight, and the amount of shared weight depends on the leaning.
Hence, if the leaning is very little, you can dance without sharing weight: you just have to keep your center of mass (which is NOT ALWAYS in the pelvis area, but depends on your position!) over your feet.
Probably this is what you mean by "leaning is an illusion", and this is what are apparently doing Geraldine and Javier in the video. They are wonderful, but it doesn't mean that this is the only way to dance tango.
Actually you can dance with weight sharing as well.
In the following video, the same dancer, Geraldine, is dancing with Gavito, seamlessly alternating CE,OE, with and without weight sharing.
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http://www.youtube.com/watch?v=N01TpzQb2Oo