I see what you are saying and feel you are correct for the most part. I don't thing that IK is defined as "the manipulation of a SINGLE MESH". If a program is capable of linking objects together, limiting movement to a defined area, and following the cause and effect rule(move the foot and the leg follows) than you have IK. Ketting you model to look and behave as a single unit is not a property of IK. IK is the rules of movment not mesh welding or ripping. IK is just a small part of what programs like Poser and Bones do for you.