Which is exactly the problem, being immovable isn't the point, but the structure of the classes in the Ki Society and offshoots encourages the assumption that being immovable is what you are learning to do (it's not, but the assumption is the problem). When people test me I'm quite capable of moving my feet, wiggling my hips, even jumping up and down without them being able to 'move me', all I've found that means is that people think they need to be 'immovable' like me when I try to teach them how. They're immediately working from a false assumption, and therefore setting themselves the wrong criteria for success.
When teaching Ki development, I stress that what we're practicing trains our ability to achieve a specific state of mind/body coordination that is recognized internally via the feelings engendered and expressed externally via demonstrable effects in response to tests. I want students to realize it's the process that drives the end-state. Too many students concentrate on the expected (in their own minds) outcome and miss that actual learning how to get there.