I would need a citation on the kubernetes control plane having any such hard limit. etcd is its own little snowflake, and I could very easily imagine it having some bad default value like that, or even kubeadm improperly configuring it

However, related to that, for big-time clusters (q.v. https://news.ycombinator.com/item?id=35174655 and https://news.ycombinator.com/item?id=25907312) one should without question move events over into their own etcd cluster: https://openai.com/research/scaling-kubernetes-to-2500-nodes...