I can certainly agree with you on what you call the "planting" of the goal actor, the prefference of the actor to maintain its position and orientation. As Poser is the only 3D app I have ever used to any appreciable extent, I just take this for granted as normal and self-evident behavior.

There were two things I was taking issue with. The first is any sugestion the the behavior of IK is varient with respect to direction (anisotropy), I am fairly certain that this does not happen.

The second issue, and I am far less certain on this point, is how Poser impliments the planting or bending of the goal actor. Once IK has been turned on the goal actor is (by default) parented to the BODY, it will translate and rotate with the BODY. Taking a shave with Ockham's rasor I would expect the goal to fixed (planted) with respect to the BODY, (to my mind) this requires no explination, it is normal Poser behavior to be expected, it does not require any secondary goal. The only thing that requires an explination is the bending once it does start to bend, not the planted behavior.

Of course just because this is the simplest explination does not mean that it is the correct explination, there may be good reasons for implimenting a secondary goal, rather than relying on standard Poser behavior that are not evidant to a none-programmer like myself. It would be interesting to see if there is some experiment that would confirm or refute the existance of a secondary goal, but I can't think of one at the moment.