"Unacceptable circumstances" are when the Panel finds something...

"Unacceptable circumstances" are when the Panel finds something is not as it should be per the Corporations Act. The whole definition of "unacceptable" isn't grey as @eshmun is trying to make out - you either do or don't have more than 20% of the company; and you either have or haven't complied with the relevant interest notification requirements.

I agree that "control" is a subjective thing (e.g. just because my wife has shares in a company that I own shares in, it doesn't mean she's going to vote the same way I do on things at the AGM), but the Corporations Act makes the assumption that if you do have an Association, then the possibility exists that you might vote the same way and therefore you need to tell all the other shareholders that this possibility exists, and not hide it.