Corporations are not supposed to be able to have no ultimate beneficial owners. If A Inc. holds 100% of B Group, B Group is not supposed to be able to own 100% of A Inc.
How effectively are these dead-end loops in corporate ownership prevented, especially when the involved entities are in different jurisdictions that might not communicate? If such a loop is discovered to have occurred, how is it usually unwound, and by whom? Who ends up with the assets?
This isn't about whether or not the arrangement is allowed, it is about what is done about it if it manages to arise or how it is prevented from arising.