It isn't a mere warning. It is strongly recommended as the upper limit.
https://www.perfectscale.io/blog/etcd-8gb
https://github.com/etcd-io/etcd/issues/9771
And yes, I agree not allowing a pluggable replacement is really stupid.
> https://github.com/etcd-io/etcd/issues/9771
> stale bot marked this as completed (by fucking closing it)
Ah, yes, what would a Kubernetes-adjacent project be without a fucking stale bot to close issues willy nilly