The CMAP spec says that the waitQueueMultiple option should be deprecated:

Why are waitQueueSize and waitQueueMultiple deprecated?

These options are not implemented across many drivers. Additionally, they have the effect of prioritizing older requests over newer requests, which is not necessarily the behavior that users want. They can also can result in cases where queue access oscillates back and forth instead of restricting access until the size drops. We may eventually pursue an alternative solutions in Advanced Pooling Behaviors.

https://github.com/mongodb/specifications/blob/master/source/connection-monitoring-and-pooling/connection-monitoring-and-pooling.rst#why-are-waitqueuesize-and-waitqueuemultiple-deprecated