In its most pristine form, APS is continuously replanning, rescheduling and resequencing. It constantly updates manufacturing operations to reflect changing market conditions, capacity constraints, etc. Expecting empty kanban containers to somehow accommodate and communicate such rapid shifts is a pipe dream. However, manufacturers shouldn't throw out the baby with the bath water. The Lean approach should always be pursued even for today's shorter windows of operational stability.
Computer systems can play a critical role even in the leanest of environments.
They should be used to accommodate major shifts in demand. Specifically, this is in the heijunka box and kanban lot sizes. A danger in continuous replanning, rescheduling and resequencing is that it destabilizes the whole supply chain. If everyone in the chain is constantly changing their plans and production, then chaos reigns. Operating in lockstep does have its advantages.