How to selectively wait for asynchronous pipelines

I have three levels of a pipelines -- pipeline A calls pipeline B which calls pipeline C. They are all called asynchronously. Pipeline A has two stages and the second stage shouldn't run until pipeline B completes. Pipeline B, on the other hand, calls pipeline C but doesn't wait for pipeline C to complete. Pipeline B is basically launching and forgetting. Here's the problem. On it's own, pipeline B launches pipeC and forgets about it. However, when pipeA calls pipeline B, pipeA won't move to the second stage until pipeB and pipeC completes when it has "Wait for all triggered pipelines" enabled. I've also tried disabling the all triggered pipeline wait and adding a dependency on pipeB via the "Add New Dependency" option. But in that case, pipeA's second stage just launches and doesn't wait at all. That almost feels like a bug in CD v9.2. In summary. How does one have a pipeline wait on its directly triggered sub pipelines but not the asynchronous pipelines that sub-pipeline may launch?