Memory-based admission control doesn't kick in with the provided config files where no max memory is configured for the pool. This is the documented behaviour and not a bug - see https://impala.apache.org/docs/build/html/topics/impala_admission.html. However, it is inconvenient since you need to specify some max memory value even if you don't want to limit the pool's share of the clusters resources (or the cluster is variable in size).
This is unfriendly. It is also confusing since there is no explicit way to enable memory-based admission control.
You can workaround by setting the pool max memory to a very high value.
To reproduce, start a minicluster with the provided configs. If you submit multiple memory-intensive queries in parallel, they will never be queued.