Daz IK system

Robinson

So the image below is a side view, ZY plane (right view).  I start with a figure at the origin, with no rotation or transforms at all.  I pin the feet.  I then drag the pelvis down a bit with ActivePose.  I notice that even though I'm only working in the ZY plane, some tortion/rotation has happened around Y (left foot is out of position slightly).  The left leg has also bent slightly more than the right.  So my figure is no longer symmetric along my chosen axis (Z in this case).

I would have thought, though I suppose it depends on the algorithm chosen, that if the mouse is constrained to only move in one plane (ZY in this case), there should be no tortion of the body when setting a pose and perfect symmetry will be maintained.  In many cases (all actually) in order to maintain no twist or side-side, I have to go and manually reset these properties afterwards.  These small changes are enough to throw off alignment in various scenarios, i.e. left foot is precisely on the floor, now it's off the floor and needs adjusting.

Am I missing something here or is the IK system in Daz3D a bit iffy?

It did occur to me thinking in terms of forces, that the IK system may interpret the mouse down as "pulling towards", which would explain it.  I'd love to know what its actually doing when I drag.