Trying to set the cluster log size via Set-ClusterLog will cause the FailoverClustering_Diagnostic event log maximum size to balloon to 18014398507384832KB. That is 18014 PB!

We have two separate Server 2019 Hyper-V Clusters that this affected. A MSFT employee on the Q&A site confirmed this also happened in her test environment.

https://docs.microsoft.com/en-us/answers/questions/154230/why-is-the-default-size-for-the-failoverclustering.html