I think the contract in the context package is that WithCancel may leak resources if cancel is not called and the parent context is cancelable but never canceled. At least, that seems to be the behavior I see in the implementation here:
Ahh. Yeah, that's unfortunate but explains this choice.
btw, I realized I'm not being entirely fair in saying it caused a bug. There would have been one anyway. If conflictsBuilder.Wait() failed, it wouldn't cancel the other two operations. It'd wait them out even though the overall operation was doomed. Maybe not a very noticeable bug under normal conditions but still not right.